Is there a mechanical regulation of bone formation in spinal fusion?

Introduction Lumbar interbody fusion using cages is one of the most reliable treatment options for degenerative spinal diseases. Currently, many cage designs are available in the market; however none of them is completely successful, as reflected by non-union rates ranging from 7 to 30%. Cages are made of very different materials (e.g. metals, polymers) and they present a large range of morphological configurations (e.g. solid, ring), leading to distinct mechanical conditions within the fusion region. Mechanical conditions are known to largely influence bone regeneration [Klein, 2003] in long bones, however their role on spinal fusion remains largely unknown. The aim of this study was to investigate how the local mechanical conditions (strains, stress, fluid flow) created by different cage designs might influence bone tissue formation during the spinal fusion process. Methods We developed an iterative computer model to simulate the time course of tissue formation during spinal fusion. The model included the vertebral bodies, the intervertebral space and a spinal cage (Fig. 1). In each time step, tissue formation was regulated by the local mechanical conditions [Prendergast, 1997] within the regenerating region, determined using finite element techniques. The temporal and spatial evolution of tissue formation was investigated for two different cage designs (a solid and a ring cage) and two different levels of stiffness: 1 (soft) and 100 (stiff) GPa. Results Bone formation and maturation started in the most inner region of the intervertebral space and extended over time to the outer region, forming a defined callus shape (Fig. 1a). Model predictions showed a strong influence of cage stiffness and configuration on the fusion outcome (Fig 1b-e). A softer cage showed a more favourable mechanical stimulation for the regeneration of bone, leading to higher amounts of bone tissue formation. For the stiffer cage, better fusion outcome was predicted with a centered solid cage compared to a ring cage (Fig. 1c & e). Stress shielding was observed in the central hollow region of the ring cage, which was more pronounced for the stiffer cage (Fig. 1c). Discussion Mechanical conditions have an influence on bone regeneration. We investigated the effect of the mechanical environment created by different cage designs on the fusion outcome. We observed that cage design, both morphology and material properties, play a key role in the mechanical conditions within the fusion region and therefore the time course of the fusion process. In the future such understanding may be used to optimize the design of spinal fusion implants to guide and foster bone formation and inter-body fusion. References [1] Klein et al., J Orthop Res, 21: 662–669, 2003. [2] Prendergast et al., J Biomech, 30, 539-548, 1997.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

A Study of 323 Asymptomatic Volunteers

Background The understanding of the individual shape and mobility of the lumbar spine are key factors for the prevention and treatment of low back pain. The influence of age and sex on the total lumbar lordosis and the range of motion as well as on different lumbar sub-regions (lower, middle and upper lordosis) in asymptomatic subjects still merits discussion, since it is essential for patient-specific treatment and evidence-based distinction between painful degenerative pathologies and asymptomatic aging. Methods and Findings A novel non-invasive measuring system was used to assess the total and local lumbar shape and its mobility of 323 asymptomatic volunteers (age: 20–75 yrs; BMI <26.0 kg/m2; males/females: 139/184). The lumbar lordosis for standing and the range of motion for maximal upper body flexion (RoF) and extension (RoE) were determined. The total lordosis was significantly reduced by approximately 20%, the RoF by 12% and the RoE by 31% in the oldest (>50 yrs) compared to the youngest age cohort (20–29 yrs). Locally, these decreases mostly occurred in the middle part of the lordosis and less towards the lumbo- sacral and thoraco-lumbar transitions. The sex only affected the RoE. Conclusions During aging, the lower lumbar spine retains its lordosis and mobility, whereas the middle part flattens and becomes less mobile. These findings lay the ground for a better understanding of the incidence of level- and age-dependent spinal disorders, and may have important implications for the clinical long-term success of different surgical interventions

The readiness of the South African private and public sector for the fourth industrial revolution

The exponential growth of technology over the past few years led to it being given prime slot at the World Economic Forum held in Davos in January 2016, with Forum founder and executive chairman Klaus Schwab coining this potentially disruptive phenomenon as the ‘Fourth Industrial Revolution’. Since then, the term Fourth Industrial Revolution (FIR) has gained ever increasing relevance and importance. Schwab (2016) emphasised that the world is on the edge of “a technological revolution that will fundamentally alter the way we live, work and relate to one another”; and that in the pure “scale, scope and complexity, the transformation will be unlike anything humankind has experienced before”. What is certain is that the FIR is predicted by many to impact significantly on jobs in the world as robotics; automation and artificial intelligence become more prolific. This shift will have a direct bearing on South Africa as well. With the challenges facing the country, such as infrastructure constraints, frequent industrial actions, rising costs and shortages of skills, the loss of further jobs should be of concern for government and the private sector alike. The outcomes of the in-depth analysis of future studies practice and theory in this research study give credence to the argument that the manner in which planning for the future of the FIR in the South African context is taking place requires profound adjustments. The development of fresh insight through the application of futures studies is essential to this planning process, as is progressively evidenced in the tendency for present day business to make collaborative decisions and strategies that are founded on and informed by futures studies. This research has tried to gain insight into the possible future of the FIR in South Africa through the creation of four scenarios towards 2035. These are outlined as follows: The Fifth Element, which is the ‘best case’ scenario, to which the country aspires; Terminator, the ‘worst case’ scenario, in which everything goes bad; The Matrix, the outlier future based on a surprising, disruptive, emerging issue; and The Day the Earth Stood Still, in which no change takes place, making it ‘business as usual’. The research furthermore endeavoured to discover the preferred future for the FIR in a South African context, as a basis for the Future Vision of the FIR in South Africa towards 2035. All through this study, Inayatullah’s (2008) pillars of futures studies were applied as a guide in mapping the present and future, further deepening and broadening the future through the development of scenarios, and, finally, transforming the future by narrowing it down to the preferred. It is up to the South African public and private sectors to determine which path is to be followed in the decisions surrounding the embrace and acceptance of the FIR as the country moves towards progress and sustainable development. Through a novel and innovative methodology, the creation of an atmosphere of trust, and the sharing of purpose, values and benefits, a national Future Vision of the FIR in South Africa towards 2035 is attainable. All stakeholders have to commit to working in co-operative partnerships, with government, society, local communities and labour striding boldly together into a world of technological, commercial, environmental and social innovation

Benchmarking of LLM Detection: Comparing Two Competing Approaches

This article gives an overview of the field of LLM text recognition. Different approaches and implemented detectors for the recognition of LLM-generated text are presented. In addition to discussing the implementations, the article focuses on benchmarking the detectors. Although there are numerous software products for the recognition of LLM-generated text, with a focus on ChatGPT-like LLMs, the quality of the recognition (recognition rate) is not clear. Furthermore, while it can be seen that scientific contributions presenting their novel approaches strive for some kind of comparison with other approaches, the construction and independence of the evaluation dataset is often not comprehensible. As a result, discrepancies in the performance evaluation of LLM detectors are often visible due to the different benchmarking datasets. This article describes the creation of an evaluation dataset and uses this dataset to investigate the different detectors. The selected detectors are benchmarked against each other

Auswärtige Sprachpolitik im Spannungsfeld von Politik, Verwaltung und Fremdsprachendidaktik: wie sich ein Instrument zur Förderung von DaF in den EU-Institutionen gewandelt hat.

Putzier A. Auswärtige Sprachpolitik im Spannungsfeld von Politik, Verwaltung und Fremdsprachendidaktik: wie sich ein Instrument zur Förderung von DaF in den EU-Institutionen gewandelt hat. Bielefeld: Universität Bielefeld; 2017

Ca2+-aktivierte Cl- -Kanäle und Cl- -Akkumulation in Sinneszellen der Ratte

Zusammenfassung In den meisten Wirbeltier-Neuronen leiten Cl-Ströme einen inhibitorischen Cl-Auswärtsstrom. Einen gegenteiligen Effekt haben Cl-Kanäle in somatosensorischen Neuronen und Riechzellen, wo sie eine Depolarisation bewirken. Bei beiden Zelltypen ist die Aktivierung des Cl-Stroms an zytoplasmatische Ca-Signale gekoppelt. So wird z.B. der Rezeptorstrom der Riechzellen zum größten Teil von einem Ca-aktivierten Cl-Kanal getragen. Obwohl Ca-aktivierte Cl-Kanäle von mehreren Arbeitsgruppen elektrophysiologisch in vielen Zellen nachgewiesen wurden, konnte bisher kein verantwortliches Gen identifiziert werden. Den Produkten der clca-Genfamilie werden allerdings die Eigenschaften Ca-aktivierter Cl-Kanäle zugeschrieben. Die bislang klonierten clca-Gene stammen allesamt aus nicht-neuronalen Geweben. In unserer Arbeitsgruppe wurde das erste neuronale Homolog, rclca1, aus dem Riechepithel der Ratte kloniert. In dieser Arbeit wurde untersucht, ob rclca1 für den Ca-aktivierten Cl-Kanal der Riechsignalkaskade kodiert. Dazu wurde das rCLCA1-Protein zunächst mittels spezifischer Antikörper biochemisch charakterisiert und mit anderen CLCA-Proteinen verglichen: rCLCA1 ist ein glykosyliertes, 125 kDa großes Membranprotein mit vier Transmembrandomänen. Es wird - wie einige andere CLCA-Proteine - proteolytisch in ein 35 kDa und ein 97 kDa-Fragment gespalten. Es wird gezeigt, dass beide Fragmente in Zilienproteinen gegenüber dem gesamten olfaktorischen Epithel schwach angereichert sind, so wie es für alle Proteine der Riechsignalkaskade beschrieben wurde. In der Immunhistochemie konnte das rCLCA1-Protein jedoch nicht in olfaktorischen Zilien, sondern in Tight-Junction-Strukturen lokalisiert werden. Die funktionelle Untersuchung ergab, dass rclca1-transfizierte Zellen zwar eine zusätzliche Cl-Leitfähigkeit erhielten, die sich jedoch grundlegend vom nativen Strom der Riechzellen unterschied. Die Untersuchung der Riechzelllinie Odora ergab schließlich, dass rCLCA1 nicht der Ca2+-aktivierte Cl-Kanal der Riechsignalkaskade sein kann, da diese Zellen zwar den bekannten Ca-aktivierten Cl-Strom zeigten, jedoch weder das rclca1-Gen noch das entsprechende Protein exprimierten. Ca-aktivierte Cl-Ströme depolarisieren somatosensorische Neurone und Riechzellen, da diese Zellen, im Gegensatz zu den meisten ZNS-Neuronen, eine besonders hohe [Cl]i besitzen. In dieser Arbeit wurde erstmalig die Fluoreszenz-Lebenszeit-Analyse verwendet, um die [Cl]i frisch dissoziierter, somatosensorischer Neurone zu bestimmen. Mit ca. 30 mM ist sie tatsächlich so hoch, dass ein Cl-Strom die Aktivierung dieser Neurone bewirken kann. Die [Cl]i der Neurone wird durch die Expression verschiedener Cl-Transportmoleküle bestimmt. In dieser Arbeit wurde mit Hilfe RT-PCR-Experimenten und Immunhistochemie gezeigt, dass weder Riechzellen noch somatosensorische Neurone die bekannten Kationen/Cl-Kotransporter zur Cl-Akkumulation exprimieren. Die Cl-Akkumulation kann in diesen Nervenzellen somit nur durch einen aktiven Cl-Transport funktionieren

Spatial pattern analysis of thicket expansion in a semi-arid savanna

Woody thickening has negative economic and ecological impacts in savannas globally. While the increase of savanna trees as a form of bush encroachment has been well studied, less is known about the increase of thicket species in savannas, which is an important phenomenon resulting in the formation of closed-canopy clumps which may exclude the grass layer over time. The early stage of thicket expansion is often initiated by a nucleating savanna species which facilitates the establishment of woody thicket pioneer species, and as the thicket clump formation expands, bush clumps increase in dominance, thereby increasing the frequency of competitive interactions and leading to a possible switch from facilitative to competitive interactions. Spatial point pattern analysis provides a useful tool to elucidate these underlying patterns and ecological processes. I used high resolution LiDAR data combined with spatial point pattern analysis to understand tree-tree interactions in a semi-arid savanna in the Eastern Cape Province of South Africa. I conducted a cluster analysis based on vegetation structural variables to distinguish different stages of woody plant encroachment from open savanna to closed canopy thicket. Using the canopy height model, I quantified the change in the grass height from open savanna to closed canopy thicket clumps as an indicator of a possible biome shift. Additionally, I used spatial point pattern analyses to investigate the effect of thicket clump formation on the composition of savanna and thicket species, the overall patterns of trees, and the associations of small thicket species with large Vachellia karroo trees, which serve as clump initiators. Finally, I examined the mortality of savanna trees across increasing stages of thicket expansion using second order spatial statistics, namely the Mark- and Pair-Correlation Functions. Results confirmed that three vegetation states, influenced by elevation, are present at the study site, representing open canopy savanna (early-stage thicket encroachment), encroached savanna with low thicket dominance (intermediate-stage thicket encroachment), and highly encroached with dominant thicket clumps (late-stage thicket encroachment). These stages showed increasing tree height, canopy cover and canopy height density, as well as decreased (but not completely absent grass layer) as thicket encroachment progresses. Spatial point pattern analysis showed, as predicted, that there was an overall aggregation of trees at small-scales within early thicket clump formation, from which I inferred that facilitative relationships may exist between trees. Contrary to my predictions, at later stages of thicket clump formation I found dominant independent patterns between savanna adults and juvenile thicket species, which may result from a combination of facilitative and competitive effects. Lastly, as expected, I found that the density of V. karroo mortality increased as thicket encroachment increased, with an overall random spatial pattern of dead V. karroo across encroachment stages. As predicted, tree mortality was randomly distributed in space in the open savanna state, and as thicket clump formation increases, tree competitive mortality became more evident, as well as decreased tree performance. Overall, the study highlights the interplay between facilitation and competition in semiarid savanna where thicket clumps are expanding. Intervention strategies are suggested to target areas of intermediate thicket clump formation, as these areas provide an opportunity to remove V. karroo before the nucleation process has enabled the establishment and increase of thicket species and to ensure the grass layer is kept productive. I conclude that the use of remote sensing and LiDAR technology holds a wide range of possibilities for monitoring and managing woody encroachment in savanna systems, however these methods need to be further refined for effective use within African savanna and thicket context, which displays high spatial aggregation making typical segmentation methods difficult.Thesis (MSc) -- Faculty of Science, Botany, 202

Am Experimentiertisch: Position und Positionierung im Chemieunterricht

Im vorliegenden Beitrag werde ich nach einigen methodischen und begrifflichen Vorüberlegungen (Kap. 2 und 3) der Frage nachgehen, mit welchen Implikationen der (unbesetzte) Chemiesaal durch seine Herrichtung und Ausstattung für Interaktion verbunden ist (Kap. 4). In einem zweiten Schritt soll anhand von vier Standbildern die Raumnutzung des Lehrers unter besonderer Berücksichtigung seiner Positionen und Posituren deskriptiv erfasst und sozialtopografisch ausgedeutet werden (Kap. 5). Abschließend erfolgt dann die Konstitutionsanalyse des Interaktionsgeschehens (Kap. 6)

Interaction of micron and nano-sized particles with cells of the dura mater.

Intervertebral total disc replacements (TDR) are used in the treatment of degenerative spinal disc disease. There are, however, concerns that they may be subject to long-term failure due to wear. The adverse effects of TDR wear have the potential to manifest in the dura mater and surrounding tissues. The aim of this study was to investigate the physiological structure of the dura mater, isolate the resident dural epithelial and stromal cells and analyse the capacity of these cells to internalise model polymer particles. The porcine dura mater was a collagen-rich structure encompassing regularly arranged fibroblastic cells within an outermost epithelial cell layer. The isolated dural epithelial cells had endothelial cell characteristics (positive for von Willebrand factor, CD31, E-cadherin and desmoplakin) and barrier functionality whereas the fibroblastic cells were positive for collagen I and III, tenascin and actin. The capacity of the dural cells to take up model particles was dependent on particle size. Nanometer sized particles readily penetrated both types of cells. However, dural fibroblasts engulfed micron-sized particles at a much higher rate than dural epithelial cells. The study suggested that dural epithelial cells may offer some barrier to the penetration of micron-sized particles but not nanometer sized particles