Dissertations / Theses on the topic 'Snake'

Algoritmer baserade på reinforcement learning har framgångsrikt tillämpats på många olika maskininlärningsproblem. I denna rapport presenterar vi hur vi implementerar varianter på deep Q-learning-algoritmer på det klassiska datorspelet Snake. Vi ämnar undersöka hur en sådan algoritm ska konfigureras för att lära sig spela Snake så bra som möjligt. För att göra detta studerar vi hur inlärningen beror på ett urval av parametrar, genom att variera dessa en och en och studera resultaten. Utifrån detta lyckas vi konstruera en algoritm som lär sig spela spelet så pass bra att den som högst får 66 poäng, vilket motsvarar att täcka 46 % av spelplanen, efter drygt fem timmars träning. Vidare så finner vi att den tränade algoritmen utan större svårigheter hanterar att hinder introduceras i spelet.
Reinforcement learning algorithms have proven to be successful at various machine learning tasks. In this paper we implement versions of deep Q-learning on the classic video game Snake. We aim to find out how this algorithm should be configured in order for it to learn to play the game as well as possible. To do this, we study how the learning performance of the algorithm depends on some of the many parameters involved, by changing one parameter at a time and recording the effects. From this we are able to set up an algorithm that learns to play the game well enough to achieve a high score of 66 points, corresponding to filling up 46\% of the playing field, after just above 5 hours of training. Further, we find that the trained algorithm can cope well with an obstacle being added to the game.

Pathogenic fungi are increasingly associated with epidemics in wildlife populations and represent a significant threat to global biodiversity. Snake fungal disease is an emerging disease caused by the fungus, Ophidiomyces ophiodiicola, and appears to be widespread in the eastern United States. Yet an evaluation of field diagnostics, and an understanding of the population-level consequences of the disease, are lacking. First, I evaluated the use of clinical signs to predict the presence of O. ophiodiicola across season and snake habitat affiliation (aquatic or terrestrial) and I compared two sampling methods to see if collection method impacts PCR result. Overall, snakes with clinical signs had a higher probability of testing positive regardless of season or habitat association. However, terrestrial snakes had a lower overall probability of testing positive for O. ophiodiicola compared to aquatic snakes. I found no significant difference between sampling methods. Second, I used Passive Integrated Transponder (PIT) telemetry, and multistate capture-mark-recapture modelling to determine if SFD affects the short-term survival, movement, and behavior of wild snakes. I found no difference in short-term survival for snakes with SFD. Snakes with SFD spend more time surface-active and have lower permanent emigration and temporary immigration rates than snakes without SFD.

Theses (M.S.)--Marshall University, 2007.
Title from document title page. Includes abstract. Includes vitae. Document formatted into pages: contains vi, 74 pages including maps. Bibliography: p.68-69.

The world has recently seen a large increase in both research and development and layman use of machine learning. Machine learning has a broad application domain, e.g, in marketing, production and finance. Although these applications have a predetermined set of rules or goals, this project deals with another aspect of machine learning which is general intelligence. During the course of the project a non-human player (known as agent) will learn how to play the game SNAKE without any outside influence or knowledge of the environment dynamics. After having the agent train for 66 hours and almost two million games an average of 16 points per game out of 35 possible were reached. This is realized by the use of reinforcement learning and deep convolutional neural networks (CNN).

This thesis includes twenty landscape paintings, primarily oil on canvas, inspired by a trip to the Hell's Canyon Country of the Snake River. The search for a personal idiom necessitated introspection, and the visual interpretation of the recalled experience required that formal issues of painting be synthesized to communicate the essential response to the landscape. The images progress from the depiction of deep space to compositions of the component parts of the landscape: trees, water, and rock.

This thesis paper examines how I turned real life experiences and observations into a fictionalized screenplay that explores the potential for vice inherent in tip-based service industry jobs. After that, I move on to the preproduction process and touch on casting, location scouting, visualization, production design, budgeting and crewing. Next I discuss how the preproduction and on-set efforts of individuals were all critical to our production. Then I chronicle the ups and downs of postproduction. Finally, I conclude with an admittedly subjective analysis of the effectiveness of the movie itself.

Snake robots have the potential of contributing vastly in areas such as rescue missions, fire-fighting and maintenance where it may either be too narrow or too dangerous for personnel to operate. This thesis reports novel results within modelling and control of snake robots as steps toward developing snake robots capable of such operations.

A survey of the various mathematical models and motion patterns for snake robots found in the published literature is presented. Both purely kinematic models and models including dynamics are investigated. More-over, different approaches to both biologically inspired locomotion and artificially generated motion patterns for snake robots are discussed.

Snakes utilize irregularities in the terrain, such as rocks and vegetation, for faster and more efficient locomotion. This motivates the development of snake robots that actively use the terrain for locomotion, i.e. obstacle aided locomotion. In order to accurately model and understand this phenomenon, this thesis presents a novel non-smooth (hybrid) mathematical model for 2D snake robots, which allows the snake robot to push against external obstacles apart from a .at ground. Subsequently, the 2D model is extended to a non-smooth 3D model. The 2D model offers an efficient platform for testing and development of planar snake robot motion patterns with obstacles, while the 3D model can be used to develop motion patterns where it is necessary to lift parts of the snake robot during locomotion. The framework of non-smooth dynamics and convex analysis is employed to be able to systematically and accurately incorporate both unilateral contact forces (from the obstacles and the ground) and spatial friction forces based on Coulomb’s law using set-valued force laws. Snake robots can easily be constructed for forward motion on a flat surface by adding passive caster wheels on the underside of the snake robot body. However, the advantage of adding wheels suffers in rougher terrains. Therefore, the models in this thesis are developed for wheel-less snake robots to aid future development of motion patterns that do not rely on passive wheels.

For numerical integration of the developed models, conventional numerical solvers can not be employed directly due to the set-valued force laws and possible instantaneous velocity changes. Therefore, we show how to implement the models for simulation with a numerical integrator called the time-stepping method. This method helps to avoid explicit changes between equations during simulation even though the system is hybrid. Both the 2D and the 3D mathematical models are verified through experiments. In particular, a back-to-back comparison between numerical simulations and experimental results is presented. The results compare very well for obstacle aided locomotion.

The problem of model-based control of the joints of a planar snake robot without wheels is also investigated. Delicate operations such as inspection and maintenance in industrial environments or performing search and rescue operations require precise control of snake robot joints. To this end, we present a controller that asymptotically stabilizes the joints of a snake robot to a desired reference trajectory. The 2D and 3D model referred to above are ideal for simulation of various snake robot motion pattern. How-ever, it is also advantageous to model the snake robot based the standard equations of motion for the dynamics of robot manipulators. This latter modelling approach is not as suited for simulation of a snake robot due to its substantial number of degrees of freedom, but a large number of control techniques are developed within this framework and these can now be employed for a snake robot. We first develop a process plant model from the standard dynamics of a robot manipulator. Then we derive a control plant model from the process plant model and develop a controller based on input-output linearization of the control plant model. The control plant model renders the controller independent of the global orientation of the snake robot as this is advantageous for the stability analysis. Asymptotic stability of the desired trajectory of the closed-loop system is shown using a formal Lyapunov-based proof. Performance of the controller is, first, tested through simulations with a smooth dynamical model and, second, with a non-smooth snake robot model with set-valued Coulomb friction.

The three main models developed in this thesis all serve important purposes. First, the 2D model is for investigating planar motion patterns by effective simulations. Second, the 3D model is for developing motion patterns that require two degrees of freedom rotational joints on the snake robot. Finally, the control plant model is employed to investigate stability and to construct a model-based controller for a planar snake robot so that its joints are accurately controlled to a desired trajectory.

Thesis (Ph. D.)--University of North Carolina at Chapel Hill, 2006.
Title from electronic title page (viewed Oct. 10, 2007). "... in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Biology." Discipline: Biology; Department/School: Biology.

Snake robots are ideally suited to highly confined environments because their small cross-sections and highly redundant kinematics allow them to enter and move through tight spaces with a high degree of dexterity. Despite these theoretical advantages, snake robots also pose a number of practical challenges that have limited their usefulness in the field. These challenges include the need to coordinate a large number of degrees of freedom, decreased system reliability due to the serially chained nature of the robot’s design, and the complex interaction of the robot’s shape with the world. This thesis makes progress towards addressing these issues with two main areas of contribution. In the first part, we provide tools for supportive autonomy in snake robots. To provide intuitive high-level autonomous behaviors, we extend our lab’s existing gait-based control framework to develop gait-based compliant control. To reliably and accurately sense the robot’s pose and shape we present new techniques for robust state estimation that leverage the redundancies in the distributed sensing capabilities of our group’s articulated snake robots. To demonstrate these contributions in a practical application, we use them to enable a snake robot to navigate a real-world underground pipe network. One of the most limiting characteristics of our snake robots (and robots in general) is the inability to precisely sense and control the torques and forces of their actuators. As such, the second part of this thesis focuses on the design and control of a new series-elastic actuated snake robot that incorporates a high performance series-elastic actuator (SEA) and torque control. After describing the novel design of the SEA, we discuss our perspective on how to incorporate torque control and series elasticity into snake robots. Finally, we demonstrate prototypes of new low impedance motions for snake robots. These motions naturally comply to obstacles and unstructured terrain, and open a new avenue of research for snake robot locomotion.

I serpenti robot sono una classe di meccanismi iper-ridondanti che appartiene alla robotica modulare. Grazie alla loro forma snella ed allungata e all'alto grado di ridondanza possono muoversi in ambienti complessi con elevata agilità. L'abilità di spostarsi, manipolare e adattarsi efficientemente ad una grande varietà di terreni li rende ideali per diverse applicazioni, come ad esempio attività di ricerca e soccorso, ispezione o ricognizione. I robot serpenti si muovono nello spazio modificando la propria forma, senza necessità di ulteriori dispositivi quali ruote od arti. Tali deformazioni, che consistono in movimenti ondulatori ciclici che generano uno spostamento dell'intero meccanismo, vengono definiti andature. La maggior parte di esse sono ispirate al mondo naturale, come lo strisciamento, il movimento laterale o il movimento a concertina, mentre altre sono create per applicazioni specifiche, come il rotolamento o l'arrampicamento. Un serpente robot con molti gradi di libertà deve essere capace di coordinare i propri giunti e reagire ad ostacoli in tempo reale per riuscire a muoversi efficacemente in ambienti complessi o non strutturati. Inoltre, aumentare la semplicità e ridurre il numero di controllori necessari alla locomozione alleggerise una struttura di controllo che potrebbe richiedere complessità per ulteriori attività specifiche. L'obiettivo di questa tesi è ottenere un comportamento autonomo cedevole che si adatti alla conformazione dell'ambiente in cui il robot si sta spostando, accrescendo le capacità di locomozione del serpente robot. Sfruttando la cedevolezza intrinseca del serpente robot utilizzato in questo lavoro, il SEA Snake, e utilizzando un controllo che combina cedevolezza attiva ad una struttura di coordinazione che ammette una decentralizzazione variabile del robot, si dimostra come tre andature possano essere modificate per ottenere una locomozione efficiente in ambienti complessi non noti a priori o non modellabili.

This thesis is motivated by the long-term goal of developing snake robots which can move in unknown and challenging environments in order to support human intervention tasks. Inspired by biological snakes, snake robots typically consist of a large number of serially connected joint modules which provide stable and robust locomotion skills. The aim of this thesis is to increase our basic understanding of snake robot locomotion and to present new control strategies for these mechanisms. The thesis contains two parts. Part I Part I considers planar snake robot locomotion across horizontal and flat surfaces. The treatment of this control problem is based on two different mathematical models of the snake robot. The first model is developed from first principles, while the second model is developed based on simplifying assumptions. The models are analysed using several techniques. A stabilizability and controllability analysis reveals fundamental properties of snake robot dynamics which have been assumed in the snake robot literature, but never formally proven. Several properties are also derived directly from the equations of motion of the robot, some of which explain why anisotropic ground friction properties are important during .at surface locomotion. An averaging analysis reveals important relationships between specific gait pattern parameters of the robot and the resulting velocity during locomotion. Two controllers for straight line path following control are proposed. By analysing a Poincaré map, all state variables of a snake robot, except for the position along the desired straight path, are shown to trace out an exponentially stable periodic orbit with the .rst controller. Using cascaded systems theory, the second controller is proved to κ-exponentially stabilize a snake robot to any desired straight path under the assumption that the forward velocity is contained in some nonzero and positive interval. Mor over, a waypoint guidance strategy is proposed for steering a snake robot along more general paths de.ned by waypoints interconnected by straight lines. The guidance strategy is guaranteed to steer the position of the robot into the acceptance region of each waypoint. Furthermore, it is outlined how the controllers can be extended to path following of general curved paths. The development of a snake robot for .at surface motion is presented, and the robot is employed to experimentally validate many of the theoretical results. Part II Part II considers snake robot locomotion in environments containing external objects (or obstacles), which is in line with practical applications of these mechanisms. A hybrid model of a planar snake robot interacting with obstacles is presented, where obstacle interaction is modelled by introducing a unilateral velocity constraint on each contacted link of the robot. The existence and uniqueness properties of the hybrid model are investigated based on the theory of linear complementarity problems. The control problem in this obstacle environment is attacked based on the notion of obstacle-aided locomotion, where the snake robot is propelled by active use of the contact forces from the obstacles. A general control principle is proposed which suggests that obstacle-aided locomotion is achieved by producing body shape changes where the links in contact with obstacles are rotated to increase the propulsive forces on the robot. This control principle is employed to propose a hybrid controller aimed at resolving situations where the snake robot is jammed between obstacles. The control principle is also instrumental in the development of a straight line path following controller in the obstacle environment, where the motion of the snake robot is speci.ed in terms of a body wave component, an environment adaptation component, and a heading control component. The development of a snake robot for motion in unstructured environments is presented. The robot, which can sense its environment due to a novel force sensing system, is employed to experimentally investigate the proposed control strategies.

When we’re talking about the field of robotics, one of the key components is the controller for the robots. The focus has recently begun shifting away from the traditional wheeled robots, into biologically inspired robots. Research is being done on walker robots with different numbers of legs, and also serpentile robots are being worked on. The previous and reasonably well-established robot controllers for the wheeled robots is generally not applicable for the new robots, since it is now a much larger focus on the motorics and how the robot must manipulate its limbs to be able to move. This opens up a new and more advanced area of research, where both navigation and movement have to be taken into consideration when making the controllers.This project will attempt to make a controller for serpentile robots using an Evolutionary Algorithm to evolve the network on its own, since this has shown promise in previous projects in the field. We also introduce a simple environment into the system to see how the system is able to handle and adjust to changes in the terrain. Primarily we will be looking at changes in elevation, but impassable terrain is also possible using the scheme we implemented. The snake robot is mainly just trying to move as far as possible in any direction, but we will also try giving it specific target destinations.Even if there was some trouble with the simulator, the project did produce positive results. We will also discuss possible ways to expand on this project, or new projects in the future.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007.
Includes bibliographical references (p. 117-121).
Snake robots have been studied by many researchers but historically more on a theoretical basis. Recently, more and more robotic snakes have been realized in hardware. This thesis presents a design process for the electrical, sensing, and mechanical systems needed to build a functional robotic snake capable of tactile and force sensing. Implementing a simple scheme which allows this capability permits the robot to laterally undulate without the use of wheels. The design methodology and implementation is detailed with schematics and a summary of results obtained from the hardware. Through manipulation of the body shape, the robot was able to move in the horizontal plane by pushing off of obstacles to create propulsive forces. It was found that lateral undulation is highly dependent on the actuator torque output and environmental friction.
by Amit Gupta.
S.M.

Theses (M.S.)--Marshall University, 2007.
Title from document title page. Includes abstract. Includes vitae. Document formatted into pages: contains v, 75,[19] pages including illustrations. Bibliography: p. 73-75.

Snakes are probably the best example of evolutionarily life-threatening stimulus as they have been one of the first predators of primates and mammals in general. In recent years, it has been shown that snake images produce specific behavioral and electrophysiological reactions in humans, provoking enhanced brain activity over the occipital cortex compared with pictures of other animals. The present study investigated the hypothesis that the response to snake images is independent from awareness. Subjects (n=27) were asked to observe pictures of threatening and non-threatening animal stimuli, presented rapidly and in random order on a screen. Awareness level was manipulated using 4 different conditions of backward masks. Event Related Potentials (ERPs) showed that activity over the occipital cortex was clearly more pronounced for snake images than for the other images, but only in unmasked condition.
Ormar är sannolikt ett av de bästa exemplen på ett evolutionärt livshotande stimuli då de utgjort ett av de första rovdjuren för primater och däggdjur i allmänhet. På senare år har man visat att bilder på ormar producerar specifika beteenden och elektrofysiologiska reaktioner hos människan, och ökad hjärnaktivitet i occipitalkortex jämfört med bilder på andra djur. Föreliggande studie undersökte hypotesen att responsen till ormbilder är oberoende från medvetandet. Deltagarna (n=27) ombads observera bilder på hotfulla respektive icke-hotfulla djurstimuli som presenterades snabbt och i slumpvis ordning på skärmen. Nivå av medvetande manipulerades genom att använda fyra olika betingelser av bakåt maskering. Event-relaterade potentialer (ERPs) visade att aktiviteten över occipitalkortex var betydligt mer uttalad för ormbilder jämfört med andra bilder, men bara i den icke-maskerade betingelsen.

Foraging mode is repeatedly invoked as a powerful and pervasive force in snake evolution, because active foragers and ambushers differ in many significant morphological, physiological, and behavioural characteristics. However, foraging mode is highly conservative phylogenetically in snakes, and most taxa that have been studied in any detail belong to one of two families: viperids (which almost all hunt by ambush) and colubrids (which are mostly active searchers). Therefore, it is difficult to know if the observed differences result from disparate foraging modes or from divergent evolutionary histories.

By comparing the European literary character Melusine with her Chinese counterpart Madam White, my thesis aims to demonstrate that the metamorphosis of females into snakes is presented in both myths as the literary reproduction of the social and historical process whereby men’s power oppressed women’s. The serpentine metamorphosis will be argued to have a mechanism, which consists of three key elements, namely a specific date, religious context, and forced metamorphosis. To do this, first, I will explore the symbolism of snakes in central European and far eastern Asian traditions. Second, in a close reading, I will analyze and compare the negative impact of serpentine metamorphoses of Melusine and Madam White in their stories. Finally, by addressing the connection to real-life contexts (social, cultural and religious) in the development of these characters, I will provide new insights into the role and status of women in China and German-speaking Europe since early modern times as well as the possible roots of their image as femmes fatales in modern literature.
Arts, Faculty of
Central Eastern Northern European Studies, Department of
Graduate

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Um certo número de proteínas do veneno foram purificadas, caracterizadas e as suas estruturas foram determinadas para delinear as suas especialidades. (a) A LAAO de Bothrops jararacussu indicou uma maior especialidade para os resíduos hidrófobos, devido a uma substituição de Trp430por lle. O FAD ligado estava em uma conformação diferente do relatado em outros estudos. (b) O domínio rico em cisteína da metaloproteinase (MP III) de Bothrops moojeni pode adotar diferentes orientações relativas. (c) O local de distribuição de carga de serino proteinases é fundamental para determinar a especificidade da enzima. (d) A conformação tetramérica da Lys49 PLA2 de Bothrops brazili indica coexistência de dois estados diméricas. (e) A adição de uma segunda ponte dissulfeto estabiliza o loop catalítico e Trp 230 adota uma conformação diferente na ligação do substrato. Estes resultados contribuem para melhorar a nossa compreensão do modo de ação e função dessas proteínas
A number of venom proteins were purified, characterized and their structures were determined to delineate their specificities. (a) The LAAO from Bothrops jararacussu indicated a higher specifity for hydrophobic residues due to a substitution of Trp430 by lle. The bound FAD was in a diferente conformation to that reported in other studies. (b) The cysteine rich domain of the metalloproteinase (MP III) from Bothrops moojeni can adopt different relative orientations. (c) The local charge distribution of serine proteinases is instrumental in determining enzyme specificity. (d) The tetrameric conformation of the Lys49 PLA2 from Bothrops brazili indicates coexistence of two dimeric states. (e) The addition of a second disulphide bridge stabilizes the catalytic loop and Trp 230 adopts a different conformation on substrate binding. These results contribute to improve our understanding of the mode of action and function of these proteins

Two-dimensional electron gases (2DEG) located at GaAs/Al0.33Ga0.67As heterojunctions are modulated by a periodic magnetic field generated by a magnetic grating fabricated at the surface of the heterostructure and are irradiated by microwaves. The devices were investigated for the detection of excitations of both paramagnetic and ferromagnetic spins in the magnetoresistance. Electron spin antiresonance was electrically detected, where spin flips are propelled by two transitions: one activated by snake orbit oscillations in the slanted magnetic field, the other by the microwaves. The double resonance forms a dark state which blocks spin flips, decreases Overhauser shift and freezes snake orbit drift, therefore changing the conduction in the 2DEG. The antiresonance is quantitatively described in the coherent population trapping framework. Collective and localised spin wave modes in dysprosium and cobalt gratings were detected as well in the 2DEG. Such effects were investigated as a function of microwave power, temperature, tilt angle of the applied magnetic field, and by varying the structural and material parameters to change the strength of dipolar interactions. The data reveal two types of spin waves. Dipolar magnetisation waves propagate across the grating through the magnetostatic interaction between stripes. An analytical expression of their dispersion curve was derived and a good fit of the ferromagnetic resonance broadening was obtained. The second type are dipolar edge spin waves which manifest through a series of sharp resonances at lower magnetic field. These waves are confined near the pole surfaces in spin wave ”wells”. The eigenfrequencies of the quantised modes were calculated and a qualitative explanation of the low field resonances was obtained. The experiments show that photovoltage measurements in hybrid semiconductor-ferromagnetic structures provide a sensitive and non-invasive tool for probing the spin waves of small magnets

Orientador: Raghuvir Krishnaswamy Arni
Banca: Patrick Jack Spencer
Banca: Adélia Cristina Oliveira Cintra
Banca: Jose Ramon Abrego
Banca: Fátima Pereira de Souza
Resumo: Um certo número de proteínas do veneno foram purificadas, caracterizadas e as suas estruturas foram determinadas para delinear as suas especialidades. (a) A LAAO de Bothrops jararacussu indicou uma maior especialidade para os resíduos hidrófobos, devido a uma substituição de Trp430por lle. O FAD ligado estava em uma conformação diferente do relatado em outros estudos. (b) O domínio rico em cisteína da metaloproteinase (MP III) de Bothrops moojeni pode adotar diferentes orientações relativas. (c) O local de distribuição de carga de serino proteinases é fundamental para determinar a especificidade da enzima. (d) A conformação tetramérica da Lys49 PLA2 de Bothrops brazili indica coexistência de dois estados diméricas. (e) A adição de uma segunda ponte dissulfeto estabiliza o loop catalítico e Trp 230 adota uma conformação diferente na ligação do substrato. Estes resultados contribuem para melhorar a nossa compreensão do modo de ação e função dessas proteínas
Abstract: A number of venom proteins were purified, characterized and their structures were determined to delineate their specificities. (a) The LAAO from Bothrops jararacussu indicated a higher specifity for hydrophobic residues due to a substitution of Trp430 by lle. The bound FAD was in a diferente conformation to that reported in other studies. (b) The cysteine rich domain of the metalloproteinase (MP III) from Bothrops moojeni can adopt different relative orientations. (c) The local charge distribution of serine proteinases is instrumental in determining enzyme specificity. (d) The tetrameric conformation of the Lys49 PLA2 from Bothrops brazili indicates coexistence of two dimeric states. (e) The addition of a second disulphide bridge stabilizes the catalytic loop and Trp 230 adopts a different conformation on substrate binding. These results contribute to improve our understanding of the mode of action and function of these proteins
Doutor

Existem milhares de espécies de serpentes no mundo, muitas com padrões distintos e intricados. Esta diversidade se torna um problema para usuários que precisam criar texturas de pele de serpente para aplicar em modelos 3D, pois a dificuldade em criar estes padrões complexos é considerável. Nós primeiramente propomos uma categorização de padrões de pele de serpentes levando em conta suas características visuais. Então apresentamos um modelo procedural capaz de sintetizar uma vasta gama de textura de padrões de pele de serpentes. O modelo usa processamento de imagem simples (tal como sintetizar bolinhas e listras) bem como autômatos celulares e geradores de ruído para criar texturas realistas para usar em renderizadores modernos. Nossos resultados mostram boa similaridade visual com pele de serpentes reais. As texturas resultantes podem ser usadas não apenas em computação gráfica, mas também em educação sobre serpentes e suas características visuais. Nós também realizamos testes com usuários para avaliar a usabilidade de nossa ferramenta. O escore da Escala de Usabilidade do Sistema foi de 85:8, sugerindo uma ferramenta de texturização altamente efetiva.
There are thousands of snake species in the world, many with intricate and distinct skin patterns. This diversity becomes a problem for users who need to create snake skin textures to apply on 3D models, as the difficulty for creating such complex patterns is considerable. We first propose a categorization of snake skin patterns considering their visual characteristics. We then present a procedural model capable of synthesizing a wide range of texture skin patterns from snakes. The model uses simple image processing (such as synthesizing spots and stripes) as well as cellular automata and noise generators to create realistic textures for use in a modern renderer. Our results show good visual similarity with real skin found in snakes. The resulting textures can be used not only for computer graphics texturing, but also in education about snakes and their visual characteristics. We have also performed a user study to assess the usability of our tool. The score from the System Usability Scale was 85:8, suggesting a highly effective texturing tool.

The venom of many snakes contains presynaptic neurotoxins (SPAN, snake presynaptic PLA2 neurotoxin), which are able to block neurotransmission and induce muscular paralysis. Structural motives are conserved across toxins, but quaternary structures vary considerably; we have therefore considered four toxins characterised by different structural complexity: Notexin (monomer), ?-bungarotoxin (heterodimer), taipoxin (trimer) e textilotoxin (pentamer). These toxins are endowed with PLA2 enzymatic activity; they hydrolyse the sn-2 ester bond of glycerophospholipids, thereby producing lysophospholipids (lysoPLs) and fatty acids. It has been shown, by using equimolar mixtures of such lipids on isolated neuromuscular junction and on cultivated neurons, that they are able to reproduce the effects of toxins: the block of neurotransmission with alteration of the morphology of nerve terminals (depletion of synaptic vesicles (SVs), swelling, alteration of mitochondria) and the formation of bulges on neurites, characterised by accumulation of specific marker of SVs. These findings have led to interpreting the toxin mechanism of action as driven by an imbalance between exocytosis and endocytosis, due to the different structural characteristics of the lipids being produced: the lysophosphatidylcholine (lysoPC) has an inverted-cone shape and remains in the external leaflet of the membrane; on the contrary, fatty acids have a cone shape and move fast to both leaflets of the membrane. Such alteration of the lipid composition of the membrane causes its deformation, which facilitates its fusion with the SVs (ie, it facilitates the transition between the hemifusion intermediate and the open pore) and at the same time inhibits endocytosis, which is necessary to recover empty vesicles and to maintain the functionality of the synapses. Similar results, with regard to the block of neurotransmission, have been obtained when testing lysoPLs with different polar heads; in particular, lysoPLs with a negative charge are able, in presence of high magnesium concentrations, to induce a triphasic pattern of paralysis (initial depression followed by increment of neurotransmitter release, and finally a progressive lowering of the muscular contraction), which is considered specific to SPANs. The phenomenon can be reversed by washing with albumin, which complexes lipids and restores the equilibrium. SPANs and their lipid products have been tested also on the neuromuscular junction of Drosophila melanogaster. In this model, however, the toxins resulted inactive. This suggests that the specific receptors, which are necessary to their action, are missing. On the contrary, the mixture of lysoPC and oleic acid (OA) causes an initial increase of their excitatory postsynaptic potential, followed by the block of neurotransmission, and the bulging of synaptic buttons. Similar to what observed on the mouse neuromuscular junction, lysoPC is the active component; its effect on the fusion of SVs is more general than that of the toxins. Significant amounts of lysoPC were detected in the saliva of hematophagous arthropods, which are at an earlier stage of the evolution process than snakes. When used in laboratory experiments, this is sufficient to cause a range of effects which are similar to those induced by the synthetic lipids. It is therefore conceivable that such lipids represent a very simple poison obtained from digestive phospholipases, from which neurotoxins could then have evolved. The effect on the probability of SV fusion is not sufficient to explain the extensive depletion which is observed after intoxication. The prolonged production of lysoPLs and fatty acids causes an alteration of the membrane permeability to calcium, which enters into the cell mainly from the external medium. This effect induces a massive fusion of SVs, also involving the reserve pool, and the alteration of cell metabolism, notably for what concern the mitochondria. Toxins conjugated with fluorophores are visible inside the neurons a few minutes after intoxication, and they colocalise with mitochondria. When used on preparations of isolated mitochondria, such toxins are able to promote the opening of the permeability transition pore with an efficiency which is directly proportional to their phospholipasic activity; similar results were obtained with mixtures of lysoPC and fatty acids. Other amphipathic molecules, with different chemical structure than lysoPC, but a broadly similar inverted-cone shape, are also able to induce a reversible block of neurotransmission, the formation of bulges in the neurons and an increase in the intracellular calcium levels, with similar kinetics to lysoPC. In particular, miltefosine and perifosine (used in anti-tumoral therapies) as well as the lysolipid derived from PAF (Platelet Activated Factor) have already been tested. The neurotoxicity of the snake phospholipases derives therefore from a high level of specificity and localisation of enzymatic activity; however, their mechanism of action is more general, as it is related to the general role of lipids in the biological membrane fusion process .
Il veleno di molti serpenti contiene neurotossine ad azione presinaptica (SPAN, snake presynaptic PLA2 neurotoxin) che sono in grado di provocare blocco della neurotrasmissione e paralisi muscolare. I motivi strutturali sono molto conservati, ma la struttura quaternaria è molto variabile; si sono perciò prese in considerazione quattro tossine di diversa complessità strutturale: notexin (monomero), ?-bungarotoxin (eterodimero), taipoxin (trimero) e textilotoxin (pentamero). Queste tossine sono dotate di attività enzimatica di tipo PLA2, cioè idrolizzano il legame estereo in posizione 2 dei glicerofosfolipidi, producendo lisofosfolipidi e acidi grassi. Utilizzando miscele equimolari di questi lipidi su giunzione neuromuscolare isolata e su neuroni in coltura si è dimostrato che essi sono in grado di riprodurre gli effetti delle tossine: blocco della neurotrasmissione con alterazione della morfologia dei terminali (deplezione delle vescicole sinaptiche, rigonfiamento, alterazione dei mitocondri) e formazione di rigonfiamenti (“bulges”) sui neuriti, caratterizzati da accumulo di proteine specifiche delle vescicole sinaptiche. Questi dati hanno portato a interpretare il meccanismo d’azione delle tossine come uno sbilanciamento tra eso ed endocitosi, dovuto alle caratteristiche strutturali dei lipidi che vengono prodotti: la lisofosfatidilcolina (lisoPC) ha forma di cono invertito e rimane confinata nel foglietto esterno della membrana, gli acidi grassi hanno forma a cono, ma si ripartiscono velocemente su entrambe i foglietti. Questa alterazione della composizione lipidica della membrana plasmatica ne provoca una deformazione che rende più facile il processo di fusione con le vescicole sinaptiche, cioè facilita la transizione tra intermedio di emifusione e poro aperto; per le stesse ragioni invece inibisce l’endocitosi, necessaria per il recupero delle vescicole stesse e il mantenimento della funzionalità della sinapsi. Analoghi risultati di blocco della neurotrasmissione sono stati ottenuti testando lisofosfolipidi con diverse teste polari; in particolare, lisolipidi dotati di carica negativa, in presenza di alte concentrazioni di magnesio, sono in grado di provocare un andamento trifasico della paralisi (iniziale depressione, facilitazione, diminuzione progressiva della contrazione muscolare) ritenuto tipico delle SPANs. Il fenomeno è reversibile mediante lavaggio con albumina, capace di complessare i lipidi e riequilibrare la situazione. Le SPANs e i loro prodotti lipidici sono stati testati anche sulla giunzione neuromuscolare di Drosophila melanogaster: le tossine sono risultate inattive in questo modello, suggerendo la mancanza di recettori specifici, necessari alla loro azione. La miscela di lisoPC e acido oleico provoca invece un iniziale aumento del potenziale post-sinaptico eccitatorio, seguito dal blocco della neurotrasmissione, e un rigonfiamento dei bottoni sinaptici. Analogamente a quanto osservato sulla giunzione neuromuscolare di topo, il componente attivo è la lisoPC e il suo effetto sulla fusione delle vescicole sinaptiche sembra essere di carattere generale. Anche animali meno evoluti dei serpenti, come alcuni insetti ematofagi, contengono nella loro saliva concentrazioni significative di lisoPC, sufficienti a provocare nei modelli sperimentali effetti analoghi a quelli osservati con i lipidi sintetici. E’ possibile che questi lipidi rappresentino una forma molto semplice di veleno ottenuto da fosfolipasi digestive, da cui si sono in seguito evolute le neurotossine. L’effetto sulla fusione delle vescicole non è sufficiente a spiegare l’estensiva deplezione che si osserva dopo l’intossicazione. La prolungata produzione di lisolipidi e acidi grassi provoca un’alterazione della permeabilità della membrana allo ione calcio, che entra nella cellula principalmente dal mezzo esterno. Questo comporta una massiccia fusione delle vescicole sinaptiche, che coinvolge anche il pool di riserva, e alterazioni del metabolismo cellulare, soprattutto a carico dei mitocondri. Tossine coniugate con fluorofori sono visibili all’interno dei neuroni dopo tempi brevi di intossicazione e colocalizzano con i mitocondri. Su preparazioni di mitocondri isolati sono in grado di promuovere l’apertura del poro di transizione della permeabilità mitocondriale con un’efficienza proporzionale alla loro attività fosfolipasica; analoghi risultati si sono ottenuti con miscele di lisoPC e acidi grassi. Blocco reversibile della neurotrasmissione, formazione di bulges nei neuroni e aumento dei livelli intracellulari di calcio sono prodotti, con cinetiche simili a quelle della lisoPC, anche da altre molecole anfipatiche di diversa struttura chimica, ma aventi una forma complessiva di cono invertito. Tra queste sono state testate miltefosina e perifosina, usate in terapia come agenti anti-tumorali, e il lisolipide derivato dal PAF (Platelet Activated Factor). La neurotossicità delle fosfolipasi di serpente deriva quindi da una elevata specificità e localizzazione dell’attività enzimatica; accanto a ciò è da considerare che la loro azione si esplica su un meccanismo che ha carattere più generale, cioè il ruolo dei lipidi nei processi di fusione delle membrane biologiche.

Background: Venomous snakebite and its effects are a source of fear for people living in southern Nepal. As a result, people have developed a negative attitude towards snakes, which can lead to human-snake conflicts that result in killing of snakes. Attempting to kill snakes increases the risk of snakebite, and actual killing of snakes contributes to loss of biodiversity. Currently, snake populations in southern Nepal are thought to be declining, but more research is needed to evaluate the conservation status of snakes. Therefore, we assessed attitudes, knowledge, and awareness of snakes and snakebite by Chitwan National Park's (CNP) buffer zone (BZ) inhabitants in an effort to better understand challenges to snake conservation and snakebite management. The results of this study have the potential to promote biodiversity conservation and increase human health in southern Nepal and beyond. Methods: We carried out face-to-face interviews of 150 randomly selected CNP BZ inhabitants, adopting a cross-sectional mixed research design and structured and semi-structured questionnaires from January-February 2013. Results: Results indicated that 43 % of respondents disliked snakes, 49 % would exterminate all venomous snakes, and 86 % feared snakes. Farmers were the most negative and teachers were the most ambivalent towards snakes. Respondents were generally unable to identify different snake species, and were almost completely unaware of the need of conserve snakes and how to prevent snakebites. Belief in a snake god, and the ability of snakes to absorb poisonous gases from the atmosphere were among many superstitions that appeared to predispose negativity towards snakes of BZ residents. Conclusion: People with predisposed negativity towards snakes were not proponents of snake conservation. Fear, negativity, ambivalence towards, and ignorance about, snakes and the need for snake conservation were strong indicators of the propensity to harm or kill snakes. It seems that if wanton killing of snakes continues, local snake populations will decline, and rare and endangered snake species may even become locally extirpated. Moreover, inappropriate perception and knowledge about snakes and snakebites may put BZ people at increased risk of venomous snakebite. Therefore, intensive, pragmatic educational efforts focused on natural history and ecology of snakes and prevention of snakebite should be undertaken in communities and at schools and universities.

In recent years, there has been a significant increase in the interest for snake like modular robots due to their superior locomotion capabilities in terms of versatility, adaptability and scalability. Passive wheeled planar snake like robots are a major category and they are being actively researched. Due to the nonholonomic constraints imposed on them, certain configurations lead to the singularity which must be avoided at all costs. Furthermore, it is vital to generate a locomotion pattern such that they can track a wide range of trajectories. All of these objectives must be accomplished smoothly and in an energy efficient manner. Studies indicate that meeting all of these requirements is a challenging problem. In this study, a novel form of the serpenoid curve is proposed in order to make the robot track arbitrary paths. A controller has been designed using the feedback linearization method. Afterwards, a new performance measure, considering both the efficiency and sustainability of the locomotion, has been proposed to evaluate the locomotion. Optimal parameters for the proposed serpenoid curve and the linear controller have been determined for efficient locomotion by running series of simulations. Relations between the locomotion performance, locomotion speed and eigenvalues of the linear controller have been demonstrated. Simulation results show striking differences between the locomotion by using the proposed serpenoid curve with optimal parameters and the locomotion by purely tracking a given path. Obtained results also indicate that the aforementioned requirements are met successfully and confirm the validity and consistency of the proposed performance measure.

I detta examensarbete undersöks tillämpligheten av speciellt anpassade kartprojektioner för projektering, byggnation, drift och underhåll av långsträcka objekt inom svensk infrastruktur. Speciellt intresse ägnas åt Snake Grid-projektionen som utvecklats av University College London i samarbete med Network Rail, som bygger och underhåller det brittiska järnvägsnätet. I samband med att man i Sverige satsar på utbyggnad och uppgradering av järnvägsnätet med höghastighetsspår, uppstår även ny mätningstekniska utmaningar då anläggningarna blir allt mer komplicerade, och toleranserna allt snävare. Projekteringen av anläggningarna utförs oftast i programvaror som antar att bygget kommer att utföras i ett tredimensionellt rum med rätvinkliga axlar, med norr och öst i ett plan och lodriktningen vinkelrätt mot detta plan. Problem uppstår när detta antagande om en platt jord möter verkligheten med en krökt jordyta och kuperad terräng. Den klassiska lösningen på problemet är att arbeta med kartprojektioner, för att på så sätt lokalt eller regionalt approximera en platt jord vid kartering och projektering. Storleken på det område som kartprojektionen är giltig för och lokala höjdförhållanden bestämmer hur stora avbildningsfelen, i form av skalförskjutningar, som mest blir i kartan. Vid rent geodetiska tillämpningar såsom kartering eller stommätning kan korrektioner påföras de insamlade mätvärdena för att justera dem till det projicerade kartplanet, men det blir mer komplicerat när det kommer till projekteringen av anläggningar, där måttsättningen ska vara korrekt och en meter på ritningen ska motsvara en meter i vekligheten. För vissa anläggningar blir de skalförskjutningar som de officiella projektionszonerna i SWEREF 99 medför alltför stora. Ett sätt att hantera det är att istället arbeta med en för den aktuella anläggningen speciellt framtagen projektion, som minimerar avbildningsfelet längsmed anläggningens geografiska utsträckning. I Storbritannien har Network Rail övergått till att hantera sina järnvägsanläggningar enligt denna princip, och har i samarbete med University College London låtit ta fram en speciell typ av projektion för ändamålet, kallad Snake Grid. Snake Grid bygger på att justera skalförskjutningarna till noll längs med en trendlinje som löper längs med anläggningen, och justerar både för avbildningsfel beroende på projektion och på höjd över ellipsoiden. Varje stambana har på så sätt tilldelats sitt eget plana referenssystem, med skalförskjutningar i närområdet reducerade till försumbar nivå. Projektörer och utsättare kan därför arbeta enligt ovan nämnda antagande om en platt jord. De frågor som utreds i detta examensarbete är dels om Snake Grid medför signifikanta fördelar jämfört med alternativa projektionsmetoder som kan objektanpassas, exempelvis Transversal Mercator, Oblik Mercator eller Konform Lambert, och dels om det finns några avgörande skillnader i arbetssätt eller organisation mellan Sverige och Storbritannien som kan påverka lämpligheten i att arbeta på detta sätt., och om fördelarna är större än nackdelarna med avseende på ökad administration och datautbyte med tredje man. För att introducera konceptet mer i detalj för svenska läsare beskrivs teorin bakom Snake Grid relativt ingående i denna rapport. Den innehåller även kortfattade beskrivningar av ett litet urval av alternativa metoder. Därefter görs en jämförande analys i form av beräkningar, av några infrastrukturprojekt med syfte att belysa vilka styrkor och svagheter de olika metoderna har och vilka nivåer av skalförskjutningar de medför. De objekt som undersökts är West Coast och East Coast Main Line, Öresundsförbindelsen, Förbifart Stockholm, Göteborg-Borås, Ostlänken och Sundsvall-Trondheim. Resultatet av beräkningarna indikerar att traditionella projektioner som Transversal och Oblik Mercator i de flesta fall kan objektanpassas med resultat på jämförbar nivå med rapporterade resultat för Snake Grid. Anpassningen av dessa traditionella metoder kräver dock specialkompetens, och även den vardagliga tillämpningen skulle ställa vissa krav på användarna. En av fördelarna med Snake Grid är att det är en färdig paketlösning med tillgång till support för användarna. I rapporten beskrivs även Network Rails uppdrag, och vilka myndigheter som är inblandade i arbetet med investeringar och underhåll för järnvägarna på den brittiska huvudön. Den befintliga geodetiska infrastrukturen i Storbritannien, i form av referenssystem, stomnät och nätverks-RTK utvärderas också. Utöver detta har också en undersökning gjorts av hur användandet av objektanpassade projektioner passar in i gällande svenska regelverk. Syftet med dessa undersökningar har varit att avgöra om det finns några avgörande skillnader mellan Sverige och Storbritannien när det gäller förutsättningarna för användandet av objektanpassade projektioner. Resultatet av denna jämförelse mellan de två länderna är att det inte finns några avgörande skillnader som skulle göra användandet av Snake Grid eller andra objektanpassade projektioner mindre lämpligt i Sverige. För att objektanpassade projektioner ska kunna användas för järnvägsprojekt i Sverige krävs dock dispenser eller justeringar av Trafikverkets gällande regelverk.
This thesis investigates the applicability of tailored map projections for the design, construction and maintenance of long objects, such as roads and railways, in Swedish infrastructure. Special emphasis is on the Snake Grid projection, developed by University College London in collaboration with Network Rail, the organization responsible for construction and maintenance of the railway network in Great Britain. The ongoing Swedish investments in expansion and upgrades of the country’s railway network poses new challenges for surveyors, as the constructions are becoming increasingly complex and tolerances more narrow. Track design is usually carried out with software with the built-in assumption that the construction will be made in a three-dimensional space with coordinate axes pointing to the north and the east, and with a vertical axis perpendicular to those. Problems arise when this flat-Earth assumption meets the reality of a curved surface and hilly terrain. The classical solution of this dilemma is to work with map projections, in order to make a local or regional approximation of a flat Earth for mapping and design purposes. The size of the projection zone and the local topography decides the maximum distortions that will be in the map. For purely geodetic purposes, such as topographic surveying or establishment of control point networks, corrections can be applied to the measurements to fit them to the projected map, but when it comes to construction design, where dimensions should be correct and one meter in the blueprint should correspond to one meter in reality, things get more complicated. For some constructions, the scale distortions on the outskirts of the official projection zones for the Swedish national grid SWEREF 99 are too large. One way to deal with that is to instead tailor a map projection, specific for that construction object, which will minimize scale distortions along the object. In Great Britain, Network Rail has adopted this approach to managing their railway network, and together with University College London developed a special kind of map projection for this purpose, known as Snake Grid. The principle of Snake grid is to force the scale to unity along a sinuous trend line, following the track geometry, and in the process adjust for scale distortions due to both projection and height above the ellipsoid. Each main line has been assigned its own horizontal coordinate system in that way, minimizing scale distortions in proximity to the tracks to a negligible level. As a result, construction designers and surveyors can work from a flat Earth assumption. This thesis deals with the questions whether the benefits of using Snake Grid are significant compared to tailoring other map projections, like Transversal Mercator, Oblique Mercator or Lambert Conformal Conic, and whether there are any large differences in methods or organization between Sweden and the UK that might influence the suitability of this approach and whether the pros outweigh the cons such as increased administration and risks in communication. To give Swedish readers a more detailed introduction to the concept, the theoretical description of Snake Grid is relatively comprehensive in this thesis. It also contains short descriptions of a small selection of alternative methods. After that, a comparative analysis of the methods is made by way of calculation, testing a few infrastructure projects to see which strengths and weaknesses the different map projections possess, and what magnitude of scale distortions can be expected. The examined projects are the West Coast and East Coast Main Lines, the Øresund bridge, the Stockholm Bypass, the Gothenburg-Borås railway, the Eastern link railway (Ostlänken) and the railway between Sundsvall and Trondheim. The results of the calculations indicate that, in most cases, traditional map projections such as Transversal or Oblique Mercator can be tailored to a project, with results comparable to reported results for the Snake Grid method. The tailoring, however, requires specialist competence that is hard to come by, and in the practical daily application it will also put some requirements on the competence of the end user. One of the advantages of Snake Grid is that it is a package solution with user support available. The thesis also describes the responsibilities of Network Rail, and which government bodies are involved in the maintenance of the British railway network. The existing geodetic infrastructure in Great Britain, in the form of reference systems, and control point networks is also described. An evaluation has also been made, whether tailored map projections can be used in accordance with current Swedish rules and regulations for road and railway construction. The purpose of these investigations has been to determine if there are any decisive differences between Sweden and the UK with regard to the regulatory circumstances surrounding the use of object specific map projections. The result of this comparison is that there are no substantial differences that would make the use of Snake Grid or other object specific map projections less suitable in Sweden. The usage of object specific projections in railway projects would however require exemptions from or changes to the current Swedish railway regulations.

This thesis seeks to demonstrate that the Maya snake emblem glyph is associated with religious specialists, instead of geographic locations, as emblem glyphs are typically understood to be. The inscriptions and the media on which the snake emblem glyph occurs will be analyzed to determine the role or function of the "Lord of the Snake." Temporal and spatial data has also been collected to aid in understanding the enigmatic glyph. The snake emblem glyph has recently been identified as originating from a broad area containing the sites of El Peru and La Corona in Guatemala, and Dzibanche, Mexico, a departure from the longstanding choice of Calakmul, Mexico. Unprovenanced snake emblem glyph texts have been cataloged under a "Site Q" designation ('Q' for the Spanish word Que, meaning "which") by Peter Mathews. Site Q is thus not securely identified geographically, which confounds efforts to designate a particular site as the snake emblem glyph site. Other problems with the snake emblem glyph, such as its geographically wide dispersal, hint that it is not a title of a particular city or region. Yet another problem is "a proper fit" between the individuals listed on unprovenanced material and individuals named at sites associated with the snake emblem glyph. It is argued that the interpretation of the snake emblem glyph differs from how emblem glyphs are presently understood. Rather than representing a physical location, the snake emblem glyph represents a mythological place or "state," containing members who legitimize their lineage (association) through ritual events such as communication with supernaturals via the vision serpent. The specialists perform rituals, scatterings, are ballplayers, and witness events. They are rarely associated with accession, which by current interpretation is implicitly tied to emblem glyphs.
M.A.
Department of Liberal and Interdisciplinary Studies
Graduate Studies;
Liberal Studies MA

Global biodiversity losses are being driven by anthropogenic pressures; the most pervasive of which is habitat loss resulting in fragmentation and population isolation. These issues are prevalent throughout Europe due to high intensity agriculture and increasing human population densities. Limitations imposed by resources and the secretive lifestyles of many species hinder the ability of conservationists to undertake status assessments and identify conservation actions. This thesis investigates the threats to an isolated population of grass snakes Natrix helvetica on the island of Jersey, providing recommendations for conservation management and recovery, whilst testing the suitability of tools for monitoring cryptic species. Grass snakes were historically widespread throughout Jersey; however, anthropogenic influences have restricted their distribution to the west and southwest. Furthermore, recent monitoring efforts have detected few individuals and their status is unknown. Intensive surveys to locate individuals combined with occupancy and N-mixture (abundance) models identified continued occupancy of semi-natural sites in the island's west and southwest, but also highlighted poor detectability of the species unless utilising a large survey effort. Therefore, a large amount of effort is required to determine absence of snakes, and declines in the population cannot be detected with reasonable power. Occupancy models were more reliable than N-mixture models, particularly due to the risks of closure violation when estimating abundance. Nonetheless, N-mixture models estimated an abundance of 48 snakes (95% CI: 23‒1279) across the study sites. Radio-tracking also provided evidence for low detection rates. Additionally snakes demonstrated small ranges (mean: 2.48 ha ± 3.54 SD), site fidelity, preferences for ranges close to paths and compost heaps, but avoided crossing roads. Snakes were positively associated with structurally complex habitats including rough grassland, dense scrub and gorse at multiple spatial scales, but negatively with open and wooded habitats. Species distribution modelling indicated similar habitat preferences to radio-tracking and poor suitability of agricultural habitats. Areas close to amphibian prey populations were also suitable whereas those with high road densities were not. A fifth of Jersey contained priority conservation areas, however almost 90% of these areas do not receive statutory protection. Those in the west and southwest should be prioritised for protection due to their proximity to extant subpopulations. Mitochondrial genes identified the population to belong to a western lineage of grass snakes Natrix helvetica helvetica, with a probable natural colonisation prior to separation from northwest France. Within Jersey, microsatellite markers identified three subpopulations, with significant differentiation between snakes in the south and west. This coincides with a dense urban area, through which connectivity needs improvement. The Jersey grass snake population can be classified as regionally Vulnerable (D2) under IUCN guidelines. The study illustrates how nature reserves are important for maintaining isolated subpopulations and the potential avenues by which statutory protection, sympathetic management practices and efforts to improve inter-reserve connectivity can contribute to conservation objectives.

The First Australian Community is one of the ancient civilizations which depended upon the available surrounding natural resources for their clothing, nutrition and healing of disease. Unfortunately, some of their traditional medicines and / or their practical applications are lost because of poor written documentation. Plants form parts of ancient remedies used by Aboriginal and Torres Strait Islander peoples to heal ailments due to their antibacterial and antiviral activities. One of these medicinal plants is Hibbertia Scandens (Snake Vine), which was used in Aboriginal Communities’ traditional medicines to treat sores and rashes. In the current study, the leaves and roots of H. scandens were extracted using solvents ranging from less polar to more polar, and these extracts were chemically profiled by HPLC and LCMS. The bioactivity of these extracts was tested against the MCF-7 breast cancer cell line using the MTT assay; four extracts of the eight showed cytotoxic activity against MCF-7, with GI50 less than 100 μg/mL after 48 hours incubation. The DCM extract from the plant roots exhibited the greatest growth inhibition potential, with the lowest GI50 (45.7 μg/mL) after treatment for 48 hours. This extract was chosen for further studies and was further separated into twelve fractions using semi-preparative HPLC; the bioactive fractions were identified by an MTT cytotoxic analysis, with four fractions (8, 9, 10 and 12) showing an anti-proliferative effect. Fraction 8 was identified as β-sitosterol (14) and fraction 12 as β-sitosterol glucoside (18) using spectroscopic techniques. β-Sitosterol was chosen for further semi-synthetic studies as it is has known anticancer activity. Seven derivatives were produced, six of which are novel analogues and their characterization was performed using several spectroscopic techniques, including 2D NMR, FT-IR, LRMS and HRMS. The growth inhibition potential of all of these derivatives was tested against two breast cancer cell lines (MCF-7 and MDA-MB-231). β-Sitosterol and four of its derivatives showed cytotoxic effects against MCF-7, while the growth of the other cell line (MDA-MB-231) was only affected by one derivative. The tetrazole (25) analogue was the most active derivative, with increased growth inhibitory activity against both breast cancer cell lines over the corresponding carboxylic acid analogue (GI50 10.67 μM against MCF-7 and 16.27 μM against MDA-MB-231). This analogue arrests both breast cancer cell lines in the G2/M phase after 72h of treatment with GI50 and GI50 × 2 concentrations, suggesting that it acts upon mitotic division.

The Sonorini is a diverse assemblage of cryptozoic to fossorial snakes. Molecular and morphological evidence is ambiguous as to whether the tribe is monophyletic or consists of two or more independent clades. Morphological analysis, using Coluber constrictor and Liochlorophis vernalis as outgroups, indicates that the genera Conopsis, Ficimia, Gyalopion, Pseudoficimia, Stenorrhina, and Sympholis form the sister group to Chilomeniscus, Chionactis, and Sonora. This clade, in turn, is sister to Scolecophis and Tantilla. The putative genera Geagras and Tantillita are nested within the Tantilla calamarina and T. taeniata species groups, respectively.Each of the three major clades contains one or more highly fossorial forms that appear to be independently derived. Morphometric and natural history data from museum specimens, field studies, and the literature indicate that taxa with highly fossorial morphologies specialize on buried prey. Sympholis is at least a part-time commensal of leaf-cutting ants that feeds on beetle grubs; Chilomeniscus is a soil burrower that feeds on burrowing roaches and vermiform beetle larvae, whereas other members of the Ficimia and Sonora clades feed on various combinations of arachnids, orthopterans, and beetle grubs. Geagras redimitus, presumably a detritus burrower, feeds on vermiform beetle larvae, whereas Scolecophis and most Tantilla feed on centipedes. At least three other Tantilla species, including T. gracilis, T. relicta, and T. vermiformis, show parallel trends towards miniaturization, fossorial morphology, and diet of insect larvae.

A snake robot will be defined herein as any multilink robot for whose shape and motion capabilities are reminiscent of a snake like PiKo [1]. PiKo is a five links snake robot with active wheels designed by SINTEF in collaboration with the Norwegian University of Science and Technology (NTNU). Researchers have been greatly interested in the development of robots like PiKo because of its shape versatility and motion capacity in difficult terrains. These skills and properties are useful for rescue teams working in earthquakes, pipe inspection operations and other utilities where access and movement in the terrain are typically difficult. When a working team decides to develop a snake robot, an important point to consider is the development of an efficient navigation system that reaches an accurate position of the robot. Technically speaking, it is prudent to design at the same time a state observer that gives us at least the real time position and velocity information of the robot body to be controlled. The relevance of this information is derived from every control action applied to the robot will require some information about the situation of the robot over time. The controller will need feedback about the robot dynamics and the effect that the control actions have caused. Typically this information has three sources: the information that comes from external sensors, that from internal sensors that transmitting to the control place the measurements from the sensors in the robot body and estimated data from a physical model. All of these feedback sources have some advantages and disadvantages. Implementing an external observer, with external sensors, will not cause space problem with sensors location in the robot body, but when the robot is working inside a pipe, underground or in another hard environment where the optical, magnetic or radio frequency contact is difficult or impossible, the information reception from an external observer is too difficult and expensive or simply impossible. Locating internal sensors in the body of the robot may solve has the problem with the measurements reception, but still pose some difficulties which must be considered by the designer. Many times space becomes a problem when locating some sensors inside the robot body due to size and weight constraints within the robot body. Basing the navigation system instead on a physical model that simulates the robot motion invites the possibility of error due to simplifications taken during the mathematical and physical development. It is impossible to develop a perfect physical model since all the variables, forces, and parameters that depend on the nature characteristics usually are random process and we can just raise a useful factor estimating the average of these effects in our concrete situation. In this thesis a navigation system with a GPS (Global Positioning System) and IMU (Inertial Measurement Unit) fusion was achieved. This navigation system will be work as long the GPS signal is available. The application of the fusion technique further reduces one order the potential errors inherent in using only the GPS navigation system. When the robot will encounter locations where the GPS signal is impossible, this thesis will present a set of tools that not being a universal solution, it will be a set of mathematical tools that depending on the case could give us an accurate navigation system. During the time the GPS signal reception is impossible, this thesis presents the development and implementation of a physical model for a snake robot with active wheels which simulates the snake robot running behavior and studies the possibility to use the trajectory estimated by the model for reaching an accurate navigation system.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Este trabalho propõe um método de extração de contornos de telhados convexos de edifícios a partir de dados de um Modelo Digital de Superfície normalizado (MDSn). A modelagem do contorno se dará através do modelo de snake balloon, onde um funcional de energia dependente de muitas variáveis será otimizado através do algoritmo de Programação Dinâmica (PD). O MDSn se mostra atrativo na aplicação de extração de contornos de telhados de edifícios, pois permite separar as regiões de edifícios da maioria das outras regiões, principalmente as mais baixas. O modelo de snake balloon pode ser interpretado como uma curva poligonal fechada que se deforma sob a ação de forças internas e externas agindo sobre o modelo. O método proposto neste trabalho utiliza algumas características apresentadas pelo MDSn para desenvolver uma estratégia de solução do problema de otimização. Uma dessas características está ligada ao fato de que os contornos de telhados de edifícios no MDSn estão associados com grandes desníveis e os pontos representativos do contorno apresentam-se sobre o edifício. Assim, para dar início ao processo de extração, bastaria colocar um único ponto semente sobre o telhado. Tal ponto se expandiria, tornando-se uma curva poligonal fechada. Até que a curva encontre o limite do telhado são necessárias várias etapas...
This work proposes a method for building convex-roof contours extraction from data of a normalized Digital Surface Model (nDSM). The contour modeling will be made by the snake balloon model, where an energy functional depending on many variables will be optimized through the Dynamic Programming algorithm (DP). The nDSM proves to be attractive in the application of building roof contour extraction, as it allows separating buildings regions from mostly other regions, especially the lowest ones. The snake balloon model can be interpreted as an polygonal closed curve that deforms under the action of internal and external forces acting on the model. The method proposed in this work uses some of the features presented by nDSM in order to develop a strategy to solve an optimization problem. One of these characteristics is related to the fact that building roof contours in a nDSM are associated with large elevation differences and representative points of the contour are presented over the building. So, to start the extraction process, it would be enough to place a single seed point on the roof. The point would expand and become a polygonal closed curve. Until the curve find the edge of the roof, several expansion stages are required... (Complete abstract click electronic access below)