Global ground strike point characteristics in negative downward lightning flashes – Part 2: Algorithm validation

At present the lightning flash density is a key input parameter for assessing the risk of occurrence of a lightning strike in a particular region of interest. Since it is known that flashes tend to have more than one ground termination point on average, the use of ground strike point densities as opposed to flash densities is more appropriate. Lightning location systems (LLSs) do not directly provide ground strike point densities. However, ingesting their observations into an algorithm that groups strokes into respective ground strike points results in the sought-after density value. The aim of this study is to assess the ability of three distinct ground strike point algorithms to correctly determine the observed ground-truth strike points. The output of the algorithms is tested against a large set of ground-truth observations taken from different regions around the world, including Austria, Brazil, France, Spain, South Africa and the United States of America. These observations are linked to the observations made by a local LLS in order to retrieve the necessary parameters of each lightning discharge, which serve as input for the algorithms. Median values of the separation distance between the first stroke in the flash and subsequent ground strike points are found to vary between 1.3 and 2.75 km. It follows that all three of the algorithms perform well, with success rates of up to about 90 % to retrieve the correct type of the strokes in the flash, i.e., whether the stroke creates a new termination point or follows a pre-existing channel. The most important factor that influences the algorithms' performance is the accuracy by which the strokes are located by the LLS. Additionally, it is shown that the strokes' peak current plays an important role, whereby strokes with a larger absolute peak current have a higher probability of being correctly classified compared to the weaker strokes.

Responding to a Pandemic: COVID-19 Projects in the Malone Center

As the scope and scale of the COVID-19 pandemic became clear in early March of 2020, the faculty of the Malone Center engaged in several projects aimed at addressing both immediate and long-term implications of COVID-19. In this article, we briefly outline the processes that we engaged in to identify areas of need, the projects that emerged, and the results of those projects. As we write, some of these projects have reached a natural termination point, whereas others continue. We identify some of the factors that led to projects that moved to implementation, as well as factors that led projects to fail to progress or to be abandoned.

Global ground strike point characteristics in negative downward lightning flashes – part 2: Algorithm validation

At present the lightning flash density is a key input parameter to assess the risk of occurrence of a lightning strike in a particular region of interest. Since it is known that flashes tend to have more than one ground termination point on average, the use of ground strike point densities as opposed to flash densities is more appropriate. Lightning location systems (LLSs) do not directly provide ground strike point densities. However, ingesting their observations into an algorithm that groups strokes in respective ground strike points results in the sought after density value. The aim of this study is to assess the ability of three distinct ground strike point algorithms to correctly determine the observed ground-truth strike points. The output of the algorithms is tested against a large set of ground-truth observations taken from different regions around the world, including Austria, Brazil, France, Spain, South Africa and the United States of America. These observations are linked to the observations made by local LLSs in order to retrieve the necessary parameters of each lightning discharge and serves as inputs for the algorithms. It follows that all three of the algorithms perform well, with success rates up to about 90 % to retrieve the correct type of the strokes in the flash, i.e., whether the stroke creates a new termination point or follows a pre-existing channel. The most important factor that influences the algorithms' performance is the accuracy by which the strokes are located by the LLS. Additionally, it is shown that the strokes' peak current plays an important role, whereby strokes with a larger absolute peak current have a higher probability of being correctly classified compared to the weaker strokes.

The superior frontal longitudinal tract: a connection between the dorsal premotor and the dorsolateral prefrontal cortices

A few studies have identified the structural connection between the premotor area and the lateral prefrontal cortex (DLPFC) as the frontal longitudinal system (FLS). This study investigated the existence of a direct segment (none U-fibre) of the superior part of the FLS (sFLS), which connects the dorsal premotor cortex (PMd) and DLPFC and analysed its asymmetry and termination point patterns. A dataset of diffusion-weighted images from 48 subjects was used for generalised q-sampling imaging tractography. Additionally, a white-fibre dissection was conducted in two right hemispheres. An analysis of spatial location, termination points, laterality, and correlation with the subjects’ gender or handedness was performed. The sFLS was found to have a deeper longitudinal bundle directly connecting the PMd and DLPFC. The bundle is referred to hereafter as the superior frontal longitudinal tract (SFLT). The SFLT was reconstructed in 100% of right and 88% of left hemispheres. It exhibited variable patterns in different subjects in their posterior terminations. In addition, it was found to possess a complicated spatial relationship with the adjacent bundles. The SFLT was revealed successfully in two cadaveric right hemispheres, where the posterior terminations were found to originate in the PMd independent of the superior longitudinal fasciculus.

The Superior Frontal Longitudinal Tract: Connection between the Dorsal Premotor and the Dorsolateral Prefrontal Cortices

The structural connection between the dorsal premotor (PMd) and the lateral prefrontal cortices (DLPFC) has been revealed, in a few studies, as the frontal longitudinal system (FLS). This study conducted a tractography analysis and a limited, postmortem, white-fiber dissection to investigate the superior FLS tract (SFLT) and analyze both its symmetry and termination point patterns. An analysis of spatial location, termination points, laterality, and correlation with the subjects’ gender or handedness was performed. SFLT was constructed in 100% of right and 88% of left hemispheres. The tracts exhibited variable patterns in different subjects in their posterior terminations. Additionally, the SFLT was found to possess a complex spatial relationship with the adjacent bundles. The SFLT was revealed successfully in two right hemispheres, where the posterior terminations were found to originate in the PMd, and its posterior terminations being totally separate from the superior longitudinal fasciculus.

Beginnings and Endings

Each temporal sequence (specifically, in language) has its own structure and dynamics, but the beginning and the ending may be said to be universally important or significant points within such a sequence. They constitute the boundaries, or frame, of the literary text, separating it—and the world it projects—from the world around us, thus playing an important role in determining its basic shape. Locating the textual point of beginning is often somewhat complex or problematic (typically more so than that of the ending), because, at least since the advent of the print era and the book format, the “main” text is accompanied—or surrounded—by other materials collectively known as paratexts (e.g., titles, epigraphs, various kinds of prefaces) that may be likened to a threshold through which the reader gradually passes from the “outside” to the “inside” of a text. Considered as a threshold, one of the beginning’s most important potential functions is to “draw us in,” or be seductive and help carry us over from the world we inhabit to the world the author has imagined. The beginning is also particularly important in creating a primacy effect, setting off our mind in a certain direction and thereby influencing our entire reception of the work. We may make a broad distinction between “orientational” and “abrupt” textual beginnings—the latter type confronting the reader with an ongoing action, without supplying preliminary information necessary for its understanding. Historically, such beginnings became widespread from the late 19th century, with the transition from realism to modernism. A phenomenon that is particularly intriguing in the context of narrative beginnings is that of the exposition, since by definition it always constitutes the beginning of the mimetic or actional sequence but is not necessarily located at the beginning of the textual sequence. Moreover, the point of transition between the exposition and the primary narrative action (or fictive present) may be considered as another kind of “beginning,” which plays an important role in how the narrative is perceived as a whole. Delimiting the ending as a textual unit involves a fundamental issue of a different kind than those relevant to beginnings: since the ending follows everything else in the text, it is difficult to consider it without considering through it, so to speak, the text as a whole. The understanding and appreciation of endings depend to a large extent on what has preceded them. But at the same time they tend to play an important role in retrospectively shaping it and often have a lasting impact on its evaluation. The critical study of the ending has paid a good deal of attention to closure, so much so that there is a widespread tendency to conflate the two concepts; it is important, however, to differentiate between them. Whereas ending refers to the text’s termination point, closure refers to the sense of an ending: that is, not to the textual termination point itself but rather to a certain effect, or perceptual quality, produced by the text. The common distinction between “closed” and “open” endings is quite crude in its basic form and should be regarded as a finely gradated and multidimensional continuum rather than a simple dichotomy. Broadly speaking, endings that tend toward the open end of the continuum are typical of modern literature (and heavily valorized by modern criticism), and like “abrupt” beginnings they testify to a desire not to accentuate the boundaries of the work of art.

Variation in the position of the conus medullaris and dural sac in adult dogs

Although it has long been stated that the level of spinal cord termination varies depending on the size of the dog, the evidence for this remains limited. The aim of this study is to investigate the position of the conus medullaris (CM) and dural sac (DS) in a population of dogs of varying size. MRIs of the thoracolumbosacral spine of 101 dogs were included. The location of CM and DS was determined on sagittal T2-weighted images and T1-weighted images, respectively, by three independent observers. The bodyweight and the back length were used as markers of size. Regression analysis showed that the termination point of the CM had a statistically significant relationship with bodyweight (R2=0.23, P<0.05). Although not statistically significant (P=0.058), a similar relationship was found between CM and back length (R2=0.21). No statistically significant relationship was found between the termination point of the DS and bodyweight (P=0.24) or back length (P=0.19). The study confirms the terminal position of the CM is dependent on size, with a more cranial position with increasing size; however, the termination point of DS remains constant irrespective of dog size.

Syndecan functions to regulate Wnt-dependent axon guidance in C. elegans

Cell adhesion molecules are key to axon guidance during development, for example specific cues can instruct axons to terminate in a specific area, or to continue growth. Syndecans are conserved cell-surface receptors that function in multiple developmental contexts. Caenorhabditis elegans with mutations in the single syndecan gene, sdn-1, exhibited errors in anterior-posterior guidance, with axons that stopped short of, or grew past their stereotypical termination point. Syndecan function was cell non-autonomous for GABAergic axon outgrowth during early development, but was likely cell autonomous to inhibit growth later in development. sdn-1 appeared to regulate the inhibitory activity of the egl-20/Wnt ligand. Removing egl-20 from sdn-1 mutants resulted in fewer animals with prematurely terminating axons. The proteoglycan modifying enzymes hse-5 and hst-2, but not hst-6, had similar effects, suggesting specific heparan sulfate modifications regulated EGL-20 axon-terminating activity. sdn-1 functioned with lin-17/Frizzled, bar-1/β-catenin and the egl-5 Hox-like transcription factor in EGL-20-depedent axon outgrowth. bar-1 was required for egl-5 expression in the most posterior GABAergic neurons. sdn-1 mutations did not eliminate egl-5 expression, but over-expression of egl-5 rescued sdn-1 phenotypes. Our results suggest syndecan is a component of Wnt-signaling events that are necessary for axons to recognize appropriate termination points.

The Effect of File Size and Type and Irrigation Solutions on the Accuracy of Electronic Apex Locators: An In Vitro Study on Canine Teeth

Measurements of the root canal during endodontic treatment have a significant influence on the course of the therapeutic process as well as on its final result in both human and veterinary medicine. The apical constriction should be the termination point for the preparation and filling of the root canal. This research was conducted with the use of a Septodont kit consisting of a small chamber filled with the examined solution in which a healthy second incisor was placed. The step back method was applied for the root canal preparation and master apical file of 30 was used. The working length was 22 mm. The examination was conducted with the use of steel as well as nickel titanium hand instruments. Different irrigation solutions and two types of apex locators were used. Measurements of the working length of the root canal showed dependence on the size of the instrument. Examinations carried out in various environments showed that analogical measurements were obtained only for sodium hypochlorite solutions. In other environments the measured sections were shortened. Comparative examinations with the use of steel instruments demonstrated insignificant measurement differences. Compared to these results, the measurements in nickel titanium group were characterized by more considerable deviations.