The function and structure of the cerebrospinal fluid outflow system

This review traces the development of our understanding of the anatomy and physiological properties of the two systems responsible for the drainage of cerebrospinal fluid (CSF) into the systemic circulation. The roles of the cranial and spinal arachnoid villi (AV) and the lymphatic outflow systems are evaluated as to the dominance of one over the other in various species and degree of animal maturation. The functional capabilities of the total CSF drainage system are presented, with evidence that the duality of the system is supported by the changes in fluid outflow dynamics in human and sub-human primates in hydrocephalus. The review also reconciles the relative importance and alterations of each of the outflow systems in a variety of clinical pathological conditions

Water and Brain Function: Effects of Hydration Status on Neurostimulation and Neurorecording

Introduction: TMS and EEG are used to study normal neurophysiology, diagnose, and treat clinical neuropsychiatric conditions, but can produce variable results or fail. Both techniques depend on electrical volume conduction, and thus brain volumes. Hydration status can affect brain volumes and functions (including cognition), but effects on these techniques are unknown. We aimed to characterize the effects of hydration on TMS, EEG, and cognitive tasks. Methods: EEG and EMG were recorded during single-pulse TMS, paired-pulse TMS, and cognitive tasks from 32 human participants on dehydrated (12-hour fast/thirst) and rehydrated (1 Liter oral water ingestion in 1 hour) testing days. Hydration status was confirmed with urinalysis. MEP, ERP, and network analyses were performed to examine responses at the muscle, brain, and higher-order functioning. Results: Rehydration decreased motor threshold (increased excitability) and shifted the motor hotspot. Significant effects on TMS measures occurred despite being re-localized and re-dosed to these new parameters. Rehydration increased SICF of the MEP, magnitudes of specific TEP peaks in inhibitory protocols, specific ERP peak magnitudes and reaction time during the cognitive task. Rehydration amplified nodal inhibition around the stimulation site in inhibitory paired-pulse networks and strengthened nodes outside the stimulation site in excitatory and CSP networks. Cognitive performance was not improved by rehydration, although similar performance was achieved with generally weaker network activity. Discussion: Results highlight differences between mild dehydration and rehydration. The rehydrated brain was easier to stimulate with TMS and produced larger responses to external and internal stimuli. This is explainable by the known physiology of body water dynamics, which encompass macroscopic and microscopic volume changes. Rehydration can shift 3D cortical positioning, decrease scalp cortex distance (bringing cortex closer to stimulator/recording electrodes), and cause astrocyte swelling-induced glutamate release. Conclusions: Previously unaccounted variables like osmolarity, astrocyte and brain volumes likely affect neurostimulation/neurorecording. Controlling for and carefully manipulating hydration may reduce variability and improve therapeutic outcomes of neurostimulation. Dehydration is common and produces less excitable circuits. Rehydration should offer a mechanism to macroscopically bring target cortical areas closer to an externally applied neurostimulation device to recruit greater volumes of tissue and microscopically favor excitability in the stimulated circuits

The foliar micromorphology and medIicinal phytochemicalpProperties of Heteropyxis Natalensis (Myrtaceae).

Masters Degree. University of KwaZulu-Natal, Durban.The use of medicinal plants as a form of therapeutic healing is an ancient tradition in various regions of the world. As a result, there is a dire need to screen medicinal plants for their unrevealed pharmacological potential. The foliar micromorphology of plants enables researchers to investigate the synthesis and location of medicinal phytocompounds. Heteropyxis natalensis is a South African medicinal plant and is traditionally used in Venda and Zulu communities to treat several illnesses. This study aimed to characterise the foliar structures of H. natalensis leaves, locate the site of secondary metabolites, determine the phytochemical composition of the leaves, and investigate the antibacterial efficacies and silver nanoparticles (AgNPs) of the methanolic extract. Emergent, young and mature leaves were examined using various microscopy techniques which confirmed the presence of non-glandular trichomes as the main external appendages of the leaves. Micrographs also revealed internal secretory cavities and crystal idioblasts. Secretory cavities were observed accumulating amorphous secretions and histochemical tests detected alkaloids, phenolics, essential oils and lipids. Qualitative phytochemical analyses were conducted on hexane, chloroform and methanol leaf extracts, and detected phenolics, alkaloids, saponins, sterols and terpenes. Crude methanolic extract was further examined using gas chromatographymass spectrometry and identified several important bioactive compounds of pharmacological value. A “green approach” was used to synthesise AgNPs using the methanolic leaf extract. Characterisation studies identified spherical particles below 100 nm in size, as well as the functional groups responsible for the capping of silver ions (Ag+). The crude methanolic extract and AgNPs were screened for their antibacterial efficacy and showed inhibition of five pathogenic bacterial strains. The results obtained in this study revealed that the phytochemical compounds present in H. natalensis leaves justify the use of this species in traditional medicine

IMPROVING VENTRICULAR CATHETER DESIGN THROUGH COMPUTATIONAL FLUID DYNAMICS

Cerebrospinal fluid (CSF) shunts are fully implantable medical devices that are used to treat patients suffering from conditions characterized by elevated intracranial pressure, such as hydrocephalus. In cases of shunt failure or malfunction, patients are often required to endure one or more revision surgeries to replace all or part of the shunt. One of the primary causes of CSF shunt failure is obstruction of the ventricular catheter, a component of the shunt system implanted directly into the brain\u27s ventricular system. This work aims to improve the design of ventricular catheters in order to reduce the incidence of catheter obstruction and thereby reduce overall shunt failure rates. Modern CSF shunts are the result of six decades of neurosurgical progress; however, in spite of revolutionary advances in engineering, the ventricular catheter remains largely unchanged in its functionality and performance from its original design. A thorough review of the history of ventricular catheter design, and the contemporary efforts to improve it, have given valuable insight into the challenges still remaining. One of the challenges is to better understand shunt flow in order to improve the flow performance of ventricular catheters. To characterize CSF flow through catheters, this work integrated computational fluid dynamics (CFD) modelling with experimental validation. A fully-parametrized, 3-dimensional CFD catheter model was developed that allowed for exploration of the geometric design features key to the catheter’s fluid dynamics. The model was validated using bench tests and advanced fluid imaging techniques, including positron emission particle tracking (PEPT). Once validated, the model served as a basis for automated, iterative parametric studies to be conducted. This involved creating a coupled framework between the CFD simulations and a parametric analysis toolkit. Sensitivity analyses and optimization studies were performed with the objective of improving catheter flow patterns. By simulating thousands of possible geometric catheter designs, much insight was gathered that can provide practical guidelines for producing optimal flow through ventricular catheters. Ultimately, those insights can lead to better quality of life for patients who require shunts, by reducing ventricular catheter obstruction rates and the need for revision surgeries

Paralinguistic vocal control of interactive media: how untapped elements of voice might enhance the role of non-speech voice input in the user's experience of multimedia.

Much interactive media development, especially commercial development, implies the dominance of the visual modality, with sound as a limited supporting channel. The development of multimedia technologies such as augmented reality and virtual reality has further revealed a distinct partiality to visual media. Sound, however, and particularly voice, have many aspects which have yet to be adequately investigated. Exploration of these aspects may show that sound can, in some respects, be superior to graphics in creating immersive and expressive interactive experiences. With this in mind, this thesis investigates the use of non-speech voice characteristics as a complementary input mechanism in controlling multimedia applications. It presents a number of projects that employ the paralinguistic elements of voice as input to interactive media including both screen-based and physical systems. These projects are used as a means of exploring the factors that seem likely to affect users’ preferences and interaction patterns during non-speech voice control. This exploration forms the basis for an examination of potential roles for paralinguistic voice input. The research includes the conceptual and practical development of the projects and a set of evaluative studies. The work submitted for Ph.D. comprises practical projects (50 percent) and a written dissertation (50 percent). The thesis aims to advance understanding of how voice can be used both on its own and in combination with other input mechanisms in controlling multimedia applications. It offers a step forward in the attempts to integrate the paralinguistic components of voice as a complementary input mode to speech input applications in order to create a synergistic combination that might let the strengths of each mode overcome the weaknesses of the other

Scaphocephaly in a select South African population: a morphometric analysis of the cranial fossae and ventricular access points.

Masters Degree. University of KwaZulu-Natal, Durban.Scaphocephaly is a cranial deformity that results from premature fusion of the sagittal suture and is characterized by an elongated and narrowed skull. Patients with this condition present with varying clinical features including frontal bossing and occipital protrusion. This study comprised two subsets, analysing different aspects related to this cranial deformity. Most morphological and morphometrical studies in patients with scaphocephaly focus on the cranial vault. Literature on the morphometry of the cranial base and its fossae in these patients is sparse. Therefore, the first subset aimed to analyse and compare the morphometry of the cranial fossae in patients with scaphocephaly. Due to varying cranial morphology among patients with these deformities, ventricular access using conventional techniques is often a challenge. Although ventricular access may not be frequently required in paediatric scaphocephalic patients, it is vital that an ideal location of the access points be established for safe ventricular catheterization. Accordingly, the second subset aimed to document the morphometry of Kocher’s and Frazier’s points in scaphocephalic patients using known craniometric and surface anatomical landmarks. Dimensions of the anterior, middle and posterior cranial fossae (ACF, MCF and PCF) were measured using select anatomical landmarks on computed tomography (CT) scans of 24 consecutive patients diagnosed with scaphocephaly between 2014 and 2020, and 14 non-affected/ normal paediatric patients selected as controls. Parameters of Kocher’s and Frazier’s points were measured in relation to known cranial surface anatomical landmarks on scans of the scaphocephalic patients utilized in subset 1. The study found that ACF and PCF are most affected in scaphocephalic patients, with elongation along the anteroposterior (AP) plane (lengths) (ACF, p=0.041 and PCF, p=0.018). Minimal changes were observed in the transverse plane (widths) in scaphocephaly versus non-affected/normal controls. Regarding subset 2, Kocher’s point was located between 91.6mm and 140mm posterior to the nasion, and between 20.5mm and 34.6mm lateral to the midline in patients with scaphocephaly. Frazier’s point was located between 60.9mm and 82.8mm superior to the inion, and 25.9mm and 41.4mm lateral to the midline. Parameters measured in the AP plane were found to be more affected than those measured lateral from the midline. This study contributes to the literature by providing novel morphometric data based on a select South African population. Data obtained could aid craniofacial surgeons in understanding which cranial fossa is most affected in scaphocephaly and to what extent, to decide on the most appropriate method of treatment. Additionally, the study concluded that the traditional landmarks used for ventricular access are relatively unreliable in scaphocephalic patients. This study provides data for neurosurgical consideration regarding ventricular catheterization procedures in patients with scaphocephaly

Topics in kernal hypothesis testing

This thesis investigates some unaddressed problems in kernel nonparametric hypothesis testing. The contributions are grouped around three main themes: Wild Bootstrap for Degenerate Kernel Tests. A wild bootstrap method for nonparametric hypothesis tests based on kernel distribution embeddings is proposed. This bootstrap method is used to construct provably consistent tests that apply to random processes. It applies to a large group of kernel tests based on V-statistics, which are degenerate under the null hypothesis, and non-degenerate elsewhere. In experiments, the wild bootstrap gives strong performance on synthetic examples, on audio data, and in performance benchmarking for the Gibbs sampler. A Kernel Test of Goodness of Fit. A nonparametric statistical test for goodness-of-fit is proposed: given a set of samples, the test determines how likely it is that these were generated from a target density function. The measure of goodness-of-fit is a divergence constructed via Stein's method using functions from a Reproducing Kernel Hilbert Space. Construction of the test is based on the wild bootstrap method. We apply our test to quantifying convergence of approximate Markov Chain Monte Carlo methods, statistical model criticism, and evaluating quality of fit vs model complexity in nonparametric density estimation. Fast Analytic Functions Based Two Sample Test. A class of nonparametric two-sample tests with a cost linear in the sample size is proposed. Two tests are given, both based on an ensemble of distances between analytic functions representing each of the distributions. Experiments on artificial benchmarks and on challenging real-world testing problems demonstrate good power/time tradeoff retained even in high dimensional problems. The main contributions to science are the following. We prove that the kernel tests based on the wild bootstrap method tightly control the type one error on the desired level and are consistent i.e. type two error drops to zero with increasing number of samples. We construct a kernel goodness of fit test that requires only knowledge of the density up to an normalizing constant. We use this test to construct first consistent test for convergence of Markov Chains and use it to quantify properties of approximate MCMC algorithms. Finally, we construct a linear time two-sample test that uses new, finite dimensional feature representation of probability measures

Spatiotemporal Granulation

This document introduces a novel theory and technique called Spatiotemporal Granulation. Through the use of spatially encoded signals, the algorithm segments spatial and temporal information, producing grains that are localized in both space and time. Well-known transformations that are derived from classical granulation, as well as new manipulations that arise are discussed, and outlined. As a means to reassemble the grains into a new configuration, we explore how granulation parameters acquire a different context, and introduce new methods for control. We present findings and limitations of this new technique, and outline some potential creative and analytical uses. The viability of Spatiotemporal Granulation is demonstrated through a software implementation titled Angkasa

Uncertain Multi-Criteria Optimization Problems

Most real-world search and optimization problems naturally involve multiple criteria as objectives. Generally, symmetry, asymmetry, and anti-symmetry are basic characteristics of binary relationships used when modeling optimization problems. Moreover, the notion of symmetry has appeared in many articles about uncertainty theories that are employed in multi-criteria problems. Different solutions may produce trade-offs (conflicting scenarios) among different objectives. A better solution with respect to one objective may compromise other objectives. There are various factors that need to be considered to address the problems in multidisciplinary research, which is critical for the overall sustainability of human development and activity. In this regard, in recent decades, decision-making theory has been the subject of intense research activities due to its wide applications in different areas. The decision-making theory approach has become an important means to provide real-time solutions to uncertainty problems. Theories such as probability theory, fuzzy set theory, type-2 fuzzy set theory, rough set, and uncertainty theory, available in the existing literature, deal with such uncertainties. Nevertheless, the uncertain multi-criteria characteristics in such problems have not yet been explored in depth, and there is much left to be achieved in this direction. Hence, different mathematical models of real-life multi-criteria optimization problems can be developed in various uncertain frameworks with special emphasis on optimization problems

A Bricolage of Critical Hermeneutics, Abductive Reasoning, and Action Research for Advancing Humanistic Values through Organization Development Practice

This is an emergent and auto-ethnographic study to find ways for the practice of organization development (OD) to recover and sustain humanism in the workplace. It begins with a literature review hermeneutically exploring the history and relevance of three modes of inquiry—hermeneutics, abductive reasoning, and action research—paratactically, which is to say, separately without overlap or reference to each other—to future OD practice. These three modes were selected from an extended literature search for non-reductive modes of inquiry that could address the range of human interests and workplace disease as I understand them. I combined my strong background reading on hermeneutics with the abductive reasoning of C. S. Peirce as two of the modes for review and also reflexively as part of my own methodology. The third mode, action research, is borrowed from the work of Kurt Lewin and his tradition in OD, known for its humanistic and democratic aims. Also included in the literature review is a report on the some of the more salient challenges and opportunities currently confronting the practice of organization development (OD) to provide a context for practical expression of my emerging discoveries. Following the literature review, I hermeneutically surfaced submerged, tacit (hidden-from-consciousness) generative connections from the confluence (flowing together) of the three modes, as they abductively emerged from within my expanding hermeneutic experience (known as a horizon) with the literature review. I then interpret the tacit relevance of that confluence through my life experience, for illuminating those OD challenges and opportunities. Finally this study integrates a sequence of critical hermeneutic and abductive processes in a participatory action research (PAR) pathway leading to plateaus of discovery and renewal through facilitation by humanistically oriented OD praxis. I conclude with five abduced interventions hypothetically drawn from personal case studies. My audience are OD practitioners inclined to develop wholistic humanism in the workplace through facilitative immersion with small groups and micro-cultures. Here they may find enlarged conceptual frames to reconceptualize OD, engage clients in transformative dialogue, and create actionable knowledge in their practice