The use of lasers for diagnosis and treatment in medical and cosmetic applications is increasing worldwide. Not all of these modalities are superficial and many require laser light to penetrate some distance into the tissue or skin to reach the treatment site. Human skin is highly scattering for light in the visible and near infrared wavelength regions, with a consequent reduction of the fluence rate. Melanin, which occurs in the epidermis of the skin, acts as an absorber in these wavelength regions and further reduces the fluence rate of light that penetrates through the epidermis to a treatment site. In vivo fluence rate measurements are not viable, but validated and calibrated computer models may play a role in predicting the fluence rate reaching the treatment site. A layered planar computer model to predict laser fluence rate at some depth into skin was developed in a commercial raytracing environment (ASAP). The model describes the properties of various skin layers and accounts for both the absorption and scattering taking place in the skin. The model was validated with optical measurements on skin-simulating phantoms in both reflectance and transmission configurations. It was shown that a planar epidermal/dermal interface is adequate for simulation purposes. In the near infrared wavelength region (676 nm), melanin (consisting of eumelanin and pheomelanin) is the major absorber of light in the epidermis. The epidermal absorption coefficient is one of the required input parameters for the computer model. The range of absorption coefficients expected for typical South African skin phototypes (ranging from photo-sensitive light skin, phototype I on the Fitzpatrick scale, to the photo-insensitive darker skin phototype V) was not available. Non-invasive diffuse reflectance spectroscopy measurements were done on 30 volunteers to establish the expected range of absorption coefficients. In the analysis it became apparent that the contributions of the eumelanin and pheomelanin must be accounted for separately, specifically for the Asian volunteers. This is a new concept that was introduced in the diffuse reflectance probe analysis. These absorption coefficient measurements were the first to be done on the expected range of skin phototypes for the South African population. Other authors dealing with diffuse reflectance probe analysis only account for the dominant eumelanin. Both the epidermal absorption coefficient and thickness are important in the prediction of the fluence rate loss. The computer model was used to evaluate the effect of the epidermal absorption coefficient (a parameter dictated by an individual’s skin phototype) and the epidermal thickness on the fluence rate loss through the skin. The epidermal absorption is strongly wavelength dependent with the higher absorption at the shorter wavelengths. In the computer model a longer wavelength of 676 nm (typical for a photodynamic treatment (PDT) of cancer) was used. For the darker skin phototypes (V) only about 30% of the initial laser fluence rate reached a depth of 200 ìm into the skin (just into the dermis). For the PDT application, results from the computer model indicated that treatment times need to be increased by as much as 50% for very dark skin phototypes when compared to that of very light phototypes. / Thesis (PhD)--University of Pretoria, 2012. / Physics / unrestricted

Joint models for the association of a longitudinal binary and a longitudinal continuous process are proposed for situations in which their association is of direct interest. The models are parameterized such that the dependence between the two processes is characterized by unconstrained regression coefficients. Bayesian variable selection techniques are used to parsimoniously model these coefficients. A Markov chain Monte Carlo (MCMC) sampling algorithm is developed for sampling from the posterior distribution, using data augmentation steps to handle missing data. Several technical issues are addressed to implement the MCMC algorithm efficiently. The models are motivated by, and are used for, the analysis of a smoking cessation clinical trial in which an important question of interest was the effect of the (exercise) treatment on the relationship between smoking cessation and weight gain.

The high prevalence and mortality of cerebrovascular disease has led to the development of several methods to measure cerebral blood flow (CBF) in vivo. One of these, arterial spin labeling (ASL), is a quantitative magnetic resonance imaging (MRI) technique with the advantage that it is completely non-invasive. The quantification of CBF using ASL requires correction for a tissue specific parameter called the brain-blood partition coefficient (BBPC). Despite regional and inter-subject variability in BBPC, the current recommended implementation of ASL uses a constant assumed value of 0.9 mL/g for all regions of the brain, all subjects, and even all species. The purpose of this dissertation is 1) to apply ASL to a novel population to answer an important clinical question in the setting of Down syndrome, 2) to demonstrate proof of concept of a rapid technique to measure BBPC in mice to improve CBF quantification, and 3) to translate the correction method by applying it to a population of healthy canines using equipment and parameters suitable for use with humans. Chapter 2 reports the results of an ASL study of adults with Down syndrome (DS). This population is unique for their extremely high prevalence of Alzheimer’s disease (AD) and very low prevalence of systemic cardiovascular risk factors like atherosclerosis and hypertension. This prompted the hypothesis that AD pathology would lead to the development of perfusion deficits in people with DS despite their healthy cardiovascular profile. The results demonstrate that perfusion is not compromised in DS participants until the middle of the 6th decade of life after which measured global CBF was reduced by 31% (p=0.029). There was also significantly higher prevalence of residual arterial signal in older participants with DS (60%) than younger DS participants (7%, p = 0.005) or non-DS controls (0%, p < 0.001). This delayed pattern of perfusion deficits in people with DS differs from observations in studies of sporadic AD suggesting that adults with DS benefit from an improved cardiovascular risk profile early in life. Chapter 3 introduces calibrated short TR recovery (CaSTRR) imaging as a rapid method to measure BBPC and its development in mice. This was prompted by the inability to account for potential changes in BBPC due to age, brain atrophy, or the accumulation of hydrophobic A-β plaques in the ASL study of people with DS in Chapter 2. The CaSTRR method reduces acquisition time of BBPC maps by 87% and measures a significantly higher BBPC in cortical gray matter (0.99±0.04 mL/g,) than white matter in the corpus callosum (0.93±0.05 mL/g, p=0.03). Furthermore, when CBF maps are corrected for BBPC, the contrast between gray and white matter regions of interest is improved by 14%. This demonstrates proof of concept for the CaSTRR technique. Chapter 4 describes the application of CaSTRR on healthy canines (age 5-8 years) using a 3T human MRI scanner. This represents a translation of the technique to a setting suitable for use with a human subject. Both CaSTRR and pCASL acquisitions were performed and further optimization brought the acquisition time of CaSTRR down to 4 minutes which is comparable to pCASL. Results again show higher BBPC in gray matter (0.83 ± 0.05 mL/g) than white matter (0.78 ± 0.04 mL/g, p = 0.007) with both values unaffected by age over the range studied. Also, gray matter CBF is negatively correlated with age (p = 0.003) and BBPC correction improved the contrast to noise ratio by 3.6% (95% confidence interval = 0.6 – 6.5%). In summary, the quantification of ASL can be improved using BBPC maps derived from the novel, rapid CaSTRR technique.

Numerous reinforced concrete buildings vulnerable to earthquake induced collapse have been constructed in seismic zones prior to the 1970s. A major contributor to building collapse is the loss of axial load carrying capacity in non-seismically detailed columns. Experimental investigations have shown that non-seismically detailed columns will only experience axial failure after shear failure and subsequent lateral shear strength degradation have occurred. Therefore, column shear failure and degrading behavior must be modeled accurately before axial collapse algorithms can be properly implemented. Furthermore, accurate modeling of the degrading lateral-load behavior of columns is needed if lateral load sharing between structural elements is to be assessed with reasonable accuracy during seismic analyses. A calibrated analytical model was developed that is capable of estimating the lateral strength degrading behavior of RC columns prone to shear failure. Existing analytical models poorly approximate nonlinear column behavior and require several nonphysical damage parameters to be defined. In contrast, the proposed calibrated model provides the engineering community with a valuable tool that only requires the input of column material and geometric properties to simulate column behavior up to loss of lateral strength. In developing the model, a database of RC columns was compiled. Parameters extracted from database column-tests were scrutinized for trends and regression models relating damage parameters to column physical properties and boundary conditions were produced. The regression models were implemented in the degrading analytical framework that was developed in this project. Two reinforced concrete columns exhibiting significant inelastic deformations prior to failing in shear were tested in support of the analytical work. A newly developed Vision System was used to track a grid of targets on the column face with a resolution of three-thousands of an inch. Surface column deformations were measured to further the understanding of the fundamental changes in column behavior that accompany shear and axial failure and validate the proposed analytical model. This research provides the engineering community with an analytical tool that can be used to perform nonlinear dynamic analysis of buildings that are at risk of collapse and help engineers improve retrofit techniques. Further insight into shear behavior attained through this project is an important step toward the development of better shear and axial degradation models for reinforced concrete columns. / text

Šiame magistro diplominiame darbe, naudojant skirtingas atstumo funkcijas ir kalibravimo lygtis, išvedami Horvico ir Tompsono įvertinio dispersijos įvertinių svoriai. Tokiu būdu, sukonstruojami aštuoni nauji Horvico ir Tompsono įvertinio dispersijos įvertiniai. Naudojant Teiloro ištiesinimo metodą pateikiamos sukonstruotų įvertinių apytikslės dispersijos ir pasiūlyti šių dispersijų įvertiniai. Be to, darbe atliekamas matematinis modeliavimas, kurio eksperimentai atlikti naudojant darbo autorės sukurtas MATLAB programas. Matematinio modeliavimo tikslas - naujus įvertinius palyginti tarpusavyje ir su standartiniu įvertiniu. Tiriama, kaip įvertinių tikslumas priklauso nuo pasirinkto imties plano. / In this master's graduation work, the weights of estimators of Horvitz & Thompson estimator of variance are defined by using some different distance function and calibration equations. In such a way, the new eight estimators of Horvitz & Thompson estimator of variance were constructed. Using the Taylor linearization method the approximate variances of the constructed estimators were derived. The estimators of the variances of these estimators are proposed as well. Also we perform here a mathematical modeling using MATLAB program. The aim of this mathematical modeling is to compare the new estimators with each other and with a standard one. We analyze also how the accuracy of estimators depends of selected sampling design.

In flying robots, stability control is often very sensitive to the actuator performances, and the software module performing the controller, is usually subjected to a long and difficult tuning phase strongly dependent on the specific actuator used. The actuators are often electric motors equipped with propellers. The motor and propeller combination performs differently for every choice of components adopted, even if they are provided by the same vendor with the same part family. The project aims to develop an intelligent actuator module for flying robots composed by a BLDC motor and a propeller, which is invariant to the specific motor and propeller adopted. By gathering the force data of the four used on a quadrocopter, the force and control signal relation could be defined and stored into the program memory of the control board. A battery monitor and a Force-PWM controller was implemented such that it takes force as input and outputs the desired PWM-signal. Tests were made on a prototype of Iqarus quadrocopter and by mounting it with ropes to the floor, it was tested on the lift-off phase. The experiment showed theoretical and practical results, which concludes that the quadrocopter maintained the ability to lift right upwards without any remaining control, assuming proper weight balance of the quadrocopter. / Inom flygande robotar, är stabilitet kontrollen oerhört känsligt till styrdonets prestation, och mjukvaru modulen som utför kontrollen, är ofta förknippad med en lång och problematisk justerings fas starkt beroende av de enskilda styrdonen. Styrdonen är ofta elektriska motorer med propeller. Motor och propeller kombinationen uppträder olika för varje val av komponent, även om komponenterna är försedda från samma återförsäljare och modell. Syftet med detta projekt är att utveckla en intelligent styrdons modul för flygande robotar, omfattad av en BLDC motor och propeller, som blir oberoende av den särskilda motor och propeller kombination som används. Genom att samla kraft data för de fyra styrdonen som används på en quadrocopter, kunde relationen mellan kraft och kontroll signal bli definierad och lagrad i program minnet för kontrol kortet. En batteri monitor och en Kraft-PWM kontroller implementerades, vilket tar kraft data som ingång och skickar ut motsvarande PWM-signal som utgång. Tester var gjorda med en prototyp av Iqarus quadrocopter och genom att binda fast den med rep till golvet, testades den för upplyfts fasen. Experimenten visade teoretiska och praktiska resultat, vilket visar att quadrocoptern bevarade förmågan att lyfta rakt uppåt utan någon övrig kontroll, förutsatt ordentlig vikt balans av quadrocoptern. / <p>Hejsan,</p><p>Detta ar den nya versionen, som ska ersatta den gamla versionen som blev uppladdad 6/11-13.</p><p>Tack,</p><p></p><p>Mvh</p><p>Amil Lafih</p>

Des mousses de polymères modèles sont élaborées à partir d’émulsions afin d’en étudier les propriétés. De telles mousses sont intéressantes dans des applications variées d’amortisseurs (sécurité passive), de filtres ou d’isolation. Les objectifs de cette étude sont de comprendre l’origine des propriétés mécaniques des mousses et d’identifier les paramètres structuraux les plus pertinents. Pour cela, la première étape consiste en la fabrication de mousses de morphologies contrôlées à partir d’émulsions monodisperses très concentrées. Par polymérisation de la phase continue des émulsions, des mousses solides modèles à taille de cellules contrôlées et de porosité ouverte sont obtenues. Ensuite la structure de ces matériaux poreux est analysée et comparée à celle des émulsions initiales. Enfin, ces mousses sont caractérisées mécaniquement en compression. Nous présentons les résultats obtenus en variant de manière contrôlée la taille des pores et leur fraction volumique et les confrontons aux modèles existants. / Polymer foams are cellular materials commonly used for safety applications in many industrial sectors (aeronautic, passive safety, gears…). To even improve their performances, the link between their structural parameters (cell sizes, density...) and their mechanical behaviour should be better understood and modelled. A way of producing such foams is to polymerize the continuous phase of highly concentrated emulsions. The advantage of such an emulsion-based strategy is that it becomes possible to take advantage of the good control over emulsion parameters (drop size, dispersed phase volume fraction, continuous phase composition) to elaborate model foams with cells and pores having narrow size distributions. The production of model foams makes it possible to determine independently the influence of each parameter on the compression modulus and to compare the results with existing models.

Les tests de coagulation actuellement disponibles en médecine vétérinaire ne parviennent pas à détecter l’état hypercoagulable de manière fiable. Les tests usuels de l’hémostase (ex : PT, PTT, antithrombine, D-dimères, etc.) n’évaluent malheureusement qu’une infime portion de la coagulation sanguine. Les tests globaux de l’hémostase, incluant la thromboélastographie et la génération de thrombine, permettent une évaluation plus complète de l’hémostase, incluant l’équilibre entre les facteurs procoagulants et anticoagulants. Ceux-ci comportent cependant encore certaines lacunes quant à leur performance diagnostique. L’étude présentée dans ce mémoire propose des modifications à la génération de thrombine conventionnelle dans le but d’identifier un état hypercoagulable chez des chiens malades. Plus précisément, nous avons comparé les effets in vitro de la thrombomoduline et de daltéparine sur la génération de thrombine réalisée chez des chiens sains et des chiens malades, pour démontrer une déficience en anticoagulants endogènes (i.e. protéine C et antithrombine) chez ces derniers. Pour se faire, 10 chiens sains et 10 chiens malades ont été sélectionnés en fonction de leur historique, examen physique et analyses sanguines. Du plasma pauvre en plaquettes a été obtenu pour chaque chien à partir de sang total citraté, aliquoté et congelé à -80 ̊Celsius pendant moins de 18 mois. La génération de thrombine a été mesurée sur le plasma décongelé à l'aide de la méthode Calibrated Automated Thrombogram. Les mesures ont d’abord été réalisées sans anticoagulant, puis avec l’addition de thrombomoduline et de trois concentrations de daltéparine (0,2, 0,4 et 0,6 U/ml). Le potentiel de thrombine endogène (ETP), le temps d’initiation (Lag time), le temps pour l’atteinte du pic (TTPeak) et le pic (Peak) ont été obtenus et analysés à l'aide d'un modèle linéaire mixte (p < 0,05). Aucune différence n’était observée entre les groupes avant l’ajout d’anticoagulants. L’ajout de thrombomoduline et de daltéparine entraînait une diminution significative de l'ETP et du Peak dans les deux groupes. Cependant, l’effet de ces deux anticoagulants étaient significativement moins marqué dans le groupe malade par rapport au groupe sain, à l'exception du Peak aux concentrations de daltéparine les plus élevées (0,4 U/ml et 0,6 U/ml). Cette modification de la génération de thrombine conventionnelle permet donc de mettre en évidence un déficit en anticoagulant endogène chez les chiens malades, chez lesquels la génération de thrombine est moins affectée par l’ajout in vitro de substances anticoagulantes. Par conséquent, effectuer la génération de thrombine avec et sans l'ajout d'anticoagulants exogènes pourrait être bénéfique pour la détection des états d'hypercoagulables chez le chien. / Current coagulation testing in veterinary medicine fails to reliably and consistently identify hypercoagulable states. Traditional coagulation assays (e.g. PT, PTT, antithrombin, D-dimers, etc.) only assess a small portion of the process of coagulation. Global coagulation assays, including thromboelastography and thrombin generation, allow a more complete evaluation of hemostasis, including the balance of procoagulant versus anticoagulant blood components. However, these tests still have shortcomings in terms of their diagnostic utility. The study presented in this thesis investigates modifications to conventional thrombin generation techniques as an attempt to better identify hypercoagulable states in sick dogs. More specifically, we aimed to compare the in vitro effects of thrombomodulin and dalteparin on thrombin generation performed in healthy dogs and dogs presented with illnesses associated with hypercoagulable states. We hypothesized that addition of these agents would demonstrate endogenous anticoagulant deficiencies (i.e. protein C and antithrombin) in sick dogs. Ten healthy dogs and ten sick dogs were selected based on history, physical examination and complete blood work. Platelet-poor plasma was obtained from citrated whole blood, aliquoted and frozen at -80 ̊Celsius for less than 18 months. Thrombin generation was measured on thawed plasma using a Calibrated Automated Thrombogram assay. Measurements were performed without anticoagulant and with the addition of thrombomodulin and dalteparin at three dilutions (0.2, 0.4 and 0.6 U/ml). Endogenous thrombin potential (ETP), lag time (Lag time), time to peak (TTPeak) and peak thrombin generation (Peak) were recorded and analyzed using a mixed linear model (p < 0.05). No difference was observed between the groups before the addition of anticoagulants. The addition of thrombomodulin and dalteparin significantly decreased ETP and Peak thrombin generation in both groups. However, the effects of both anticoagulants were significantly less in the diseased group compared to the healthy group, except for Peak at the highest dalteparin concentrations (0.4 U/ ml and 0.6 U/ml). The addition of thrombomodulin and dalteparin to plasma in vitro highlights an endogenous anticoagulant deficiency in this population of sick dogs, by failing to reduce thrombin generation to the same extent as in healthy dogs. Therefore, performing thrombin generation with and without the addition of exogenous anticoagulants might be beneficial for the detection of hypercoagulable states in the dog.

Real-time crash prediction is a complex task, since there is no existing framework to predict crash likelihood, types, and severity together along with a real-time traffic management strategy. Developing such a framework presents various challenges, including not independent and identically distributed data, imbalanced data, large model size, high computational cost, missing data, sensitivity vs. false alarm rate (FAR) trade-offs, estimation of traffic restoration time after crash occurrence, and real-world deployment strategy. A novel spatial ensemble distillation learning modeling technique is proposed to address these challenges. First, large-scale real-time data were used to develop a crash likelihood prediction model. Second, the proposed crash likelihood model's viability in predicting specific crash types was tested for real-world applications. Third, the framework was extended to predict crash severity in real-time, categorizing crashes into four levels. The results demonstrated strong performance with sensitivities of 90.35%, 94.80%, and 84.23% for all crashes, rear-end crashes, and sideswipe/angle crashes, and 83.32%, 81.25%, 83.08%, and 84.59% for fatal, severe, minor injury, and PDO crashes, respectively, all while remaining very low FARs. This methodology can also reduce model size, lower computation costs, improve sensitivity, and decrease FAR. These results will be used by traffic management center for taking measures to prevent crashes in real-time through active traffic management strategies. The framework was further extended for efficient traffic management after any crash occurrence despite adopting these strategies. Particularly, the framework was extended to predict the traffic state after a crash, predict the traffic restoration time based on the estimated post-crash traffic state, and apply a three-step validation technique to evaluate the performance of the developed approach. Finally, real-world deployment strategies of the proposed methodologies for real-time crash prediction along with their types and severities and real-time post-crash management are discussed. Overall, the methodologies presented in this dissertation offer multifaceted novel contributions and have excellent potential to reduce fatalities and injuries.

Les études d’imagerie par résonance magnétique fonctionnelle (IRMf) ont pour prémisse générale l’idée que le signal BOLD peut être utilisé comme un succédané direct de l’activation neurale. Les études portant sur le vieillissement cognitif souvent comparent directement l’amplitude et l’étendue du signal BOLD entre des groupes de personnes jeunes et âgés. Ces études comportent donc un a priori additionnel selon lequel la relation entre l’activité neurale et la réponse hémodynamique à laquelle cette activité donne lieu restent inchangée par le vieillissement. Cependant, le signal BOLD provient d’une combinaison ambiguë de changements de métabolisme oxydatif, de flux et de volume sanguin. De plus, certaines études ont démontré que plusieurs des facteurs influençant les propriétés du signal BOLD subissent des changements lors du vieillissement. L’acquisition d’information physiologiquement spécifique comme le flux sanguin cérébral et le métabolisme oxydatif permettrait de mieux comprendre les changements qui sous-tendent le contraste BOLD, ainsi que les altérations physiologiques et cognitives propres au vieillissement. Le travail présenté ici démontre l’application de nouvelles techniques permettant de mesurer le métabolisme oxydatif au repos, ainsi que pendant l’exécution d’une tâche. Ces techniques représentent des extensions de méthodes d’IRMf calibrée existantes. La première méthode présentée est une généralisation des modèles existants pour l’estimation du métabolisme oxydatif évoqué par une tâche, permettant de prendre en compte tant des changements arbitraires en flux sanguin que des changements en concentrations sanguine d’O2. Des améliorations en terme de robustesse et de précisions sont démontrées dans la matière grise et le cortex visuel lorsque cette méthode est combinée à une manipulation respiratoire incluant une composante d’hypercapnie et d’hyperoxie. Le seconde technique présentée ici est une extension de la première et utilise une combinaison de manipulations respiratoires incluant l’hypercapnie, l’hyperoxie et l’administration simultanée des deux afin d’obtenir des valeurs expérimentales de la fraction d’extraction d’oxygène et du métabolisme oxydatif au repos. Dans la deuxième partie de cette thèse, les changements vasculaires et métaboliques liés à l’âge sont explorés dans un groupe de jeunes et aînés, grâce au cadre conceptuel de l’IRMf calibrée, combiné à une manipulation respiratoire d’hypercapnie et une tâche modifiée de Stroop. Des changements de flux sanguin au repos, de réactivité vasculaire au CO2 et de paramètre de calibration M ont été identifiés chez les aînés. Les biais affectant les mesures de signal BOLD obtenues chez les participants âgés découlant de ces changements physiologiques sont de plus discutés. Finalement, la relation entre ces changements cérébraux et la performance dans la tâche de Stroop, la santé vasculaire centrale et la condition cardiovasculaire est explorée. Les résultats présentés ici sont en accord avec l’hypothèse selon laquelle une meilleure condition cardiovasculaire est associée à une meilleure fonction vasculaire centrale, contribuant ainsi à l’amélioration de la santé vasculaire cérébrale et cognitive. / Functional MRI (fMRI) studies using the BOLD signal are done under the general assumption that the BOLD signal can be used as a direct index of neuronal activation. Studies of cognitive aging often compare BOLD signal amplitude and extent directly between younger and older groups, with the additional assumption that the relationship between neuronal activity and the hemodynamic response is unchanged across the lifespan. However, BOLD signal arises from an ambiguous mixture of changes in oxidative metabolism, blood flow and blood volume. Furthermore, previous studies have shown that several BOLD signal components may be changed during aging. More physiologically-specific information on blood flow and oxidative metabolism would allow a better understanding of these signal changes and of the physiological and cognitive changes seen with aging. The work presented here demonstrates techniques to estimate oxidative metabolism at rest and during performance of a task. These techniques are extensions of previous calibrated fMRI methods and the first method presented is based on a generalization of previous models to take into account both arbitrary changes in blood flow and blood O2 content. The improved robustness and accuracy of this method, when used with a combined hypercapnia and hyperoxia breathing manipulation, is demonstrated in visual cortex and grey matter. The second technique presented builds on the generalization of the model and uses a combination of breathing manipulations including hypercapnia, hyperoxia and both simultaneously, to obtain experimentally-determined values of resting oxygen extraction fraction and oxidative metabolism. In the second part of this thesis, age-related vascular and metabolic changes are explored in a group of younger and older adults using a calibrated fMRI framework with a hypercapnia breathing manipulation and a modified Stroop task. Changes in baseline blood flow, vascular reactivity to the CO2 challenge and calibration parameter M were identified in the older participants. Potential biases in BOLD signal measurements in older adults arising from these physiological changes are discussed. Finally, the relationship between these cerebral changes and performance on the modified Stroop task, central vascular health and cardiovascular fitness are explored. The results of this thesis support the hypothesis that greater cardiovascular fitness is associated with improvements in central vascular function, contributing in turn to improved brain vascular health and cognition.