1,350 research outputs found
The impact of kombi-taxis on public transport
No full textIncludes bibliography.This thesis attempts to quantify the impact of kombi-taxis on the conventional modes of public transport, in particular the bus, in the Cape Town Metropolitan Area. The impact is quantified in terms of the resultant modal shift of commuters from the buses, trains, cars and walking, in favour of the kombi-taxi. The approach adopted involved a study of the kombi-taxi and bus operations and characteristics on the different kombi-taxi routes in the study area. Five representative routes were selected for a detailed study, involving an Observation survey and an Interview survey directed at the bus and kombi-taxi users on these routes. On a further 66 routes, a bus-taxi modal split survey was conducted. The findings of the study show• that the majority of present kombi-taxi users are former bus users. Conservatively, an estimated 30.6% of all the daily bus passenger trips have been lost to the kombi-taxi. The effect on trains has not been insignificant with an estimated 4.4% of all commuter train trips having been converted to kombi-taxi trips
'Boda boda' bicycle taxis and their role in urban transport systems : case studies of Nakuru and Kisumu, Kenya
No full textIncludes abstract.Includes bibliographical references (leaves 117-120).The bicycle taxi has a padded cushion fitted onto a reinforced rear seat; typically removed when transporting goods. The research aimed, firstly, to understand the operating characteristics of, and challenges facing, ‘boda boda’ services, and secondly, to explore the measures that might be formulated by the concerned authorities to manage and support them. With regard to the latter aim, given the growth in motorcycle taxis at the expense of bicycle taxis elsewhere in the region, the research sought to make a recommendation on whether authorities should embrace or resist this trend
Taxis-Based Motion Control of Biohybrid Microrobots
No full textMiniaturization of on-board actuation and powering engenders the proliferation of biohybrid microrobots, which integrate motile bacteria or cells with synthetic functional components to achieve micron-scale actuations. Flagellated bacteria like S. marcescens are among the leading candidates for the actuators of swimming microrobots. However, the high intrinsic stochasticity in bacteria-driven microrobots severely limits their potential applications, such as targeted drug delivery. Taxis behaviors (e.g., chemotaxis), which help free-swimming bacteria to navigate towards favorable environments and away from hazardous ones, may offer an elegant means to control the motion of bacteria-driven microrobots. Therefore, this thesis focuses on: (a) addressing the motion guiding of bacteria-driven microrobots using common bacterial taxis behaviors, specifically chemotaxis and pH-taxis, (b) explaining the physical mechanisms associated with the tactic motions in bacteria-driven microrobots, and (c) developing a biophysical model to describe the bacterial propulsion and the chemotaxis in bacteria-driven microrobots. In order to produce considerable chemotactic motion in bacteria-driven microrobots, an appropriate chemical concentration profile needs to be determined, which requires the knowledge of the chemotaxis response of the integrated bacterial species. Thus, we first propose an experimental and modeling framework to characterize bacterial chemotaxis. The chemotaxis response of a species against a chemoattractant is experimentally quantified under a linear concentration gradient of the attractant. A signaling pathway model is fitted to the experimental measurements over a series of gradients to determine the species-specific parameters in the model, thereby fulfilling an analytical characterization of the chemotaxis. Subsequently, in a multi-bacteria-driven microrobotic system, we quantify the chemotactic drift of the microrobotic swarms towards a potent chemoattractant L-serine and elucidate the physical mechanisms associated with the drift motion by statistical trajectory analysis. It shows that the microrobots have an apparent heading preference for moving up the gradient, which constitutes the major factor that produces the chemotactic drift. The apparent heading bias is caused by a higher persistence in the heading direction when a microrobot moves up the the L-serine gradient compared to traveling down the gradient. Besides chemotaxis, we explore the potential of utilizing ambient pH to guide the motion of the bacteria-driven microrobots. Under three different pH gradients, we demonstrate that the microrobots exhibit both unidirectional and bidirectional pH-tactic behaviors. Two factors, a swimming heading bias and a speed bias, are found to be responsible for the pH-tactic motion while the heading bias contributes more. Like in chemotaxis, the heading directions of the microrobots are also significantly more persistent when they move towards favored pH regions. Finally, a biophysical model is developed to describe the bacterial propulsion and the chemotaxis in an extensively adopted design of bacteria-driven microrobots. The model traces helical trajectories and chemotactic motion that resemble those observed from experiments, which validates the basic correctness of the model. The model simulation also suggests that the seemingly collective chemotaxis among the multiple bacteria attached to a microrobot could be explained by a synchronized signaling pathway response among these bacteria. Furthermore, we investigate the dependencies of the microrobots’ per</p
Taxis Dispatch: Minimizing waiting times by maximizing coverage
No full textIn this thesis, we investigate whether maximizing the coverage of taxis can be beneficial when the goal is to minimize the waiting times of the clients. When dispatching taxis, often only current requests are taken into account and not future ones. We examined how beneficial it can be to take coverage into account. For taxi companies it is important to keep their customers satisfied, by serving them as quickly as possible. Often companies assign the taxis to the nearest requests. We investigate whether there are better dispatch methods. We developed three dispatch policies which use ILP models, and discussed what the best option is. The first policy does not consider the coverage and minimizes the waiting times of the clients among the requests that are taking place at that moment. The second one aims to maintain a good coverage and short waiting times when assigning taxis to requests. The third one also aims to maintain a good coverage and short waiting times when assigning taxis to requests and also relocates taxis to gain a better covered area. Those policies can be a contribution for taxi companies because they help to serve clients more quickly. To determine what the best way is of dispatching taxis, we run a simulation on the different policies on a real-data map and compared the results. The literature over taxi dispatch mostly conducts research on a small area like a city or a village. In this thesis, taxis dispatch takes place on a larger area where taxis commute between cities
Taxicab regulation and urban residents' use and perception of taxi services: a survey in eight cities
No full text1. Several market failures would justify some forms of price control and entry regulation in the taxicab industry. Unfortunately, history shows that very often the taxi regulators get captured by taxi operators' lobbies and fail to adapt their regulation to changing market conditions. Hence, faced with a sclerotic service supply, several cities and countries have thoroughly deregulated their taxi industry... only to gradually bring back some elements of regulation later on. Since the late 1960s academics have at length debated the pros and cons of price and entry regulations for the taxi market, either using very simplified models of selected segments of the market or referring to empirical data comparing service supply before and after deregulation in one or in several case studies. Because of the paucity of available data on the demand side, most of these empirical studies generally only consider the supply side, overlooking the impact of regulation or deregulation on taxi use and on the perception of taxi services by their clients. We have selected eight capital cities with contrasting regulatory systems and carried out a survey among their residents to understand why and how they use taxis and to collect their opinion about the quality of the service provided. Some 3200 respondents answered about 40 questions. Taxi use varies greatly from one city to the other, both in terms of trip frequency and of trip purposes. A statistical analysis of the results enabled us to draw some conclusions about the impacts of various elements of taxicab regulation on the mobility of urban residents.taxi; regulation; deregulation; mobility; London; Paris; New York; Amsterdam; Dublin; Berlin; Stockholm; Lisbon
Taxis limiting borders
No full textБобкова Елена Александровна, кандидат филологических наук, доцент кафедры английской филологии, Бирский филиал Башкирского государственного университета (г. Бирск), [email protected]. E.A. Bobkova, Bashkir State University, Birsk Affiliation, Birsk, Russian Federation, [email protected]Раскрываются некоторые аспекты категории таксиса на материале английского языка,
упоминаются несколько научных школ, занимающихся проблемой таксиса, отмечается связь
таксиса с другими темпоральными категориями – времени, вида, временной отнесенности;
возможность передачи нескольких таксисных ситуаций, образующих разные временные периоды в рамках одного предложения. Предлагается расширение границ таксиса за счет включения в таксисные отношения конструкций с придаточным изъяснительным в модусдиктумных комплексах в режиме нарратива при несовпадении времени модуса с моментом
речи как точкой отсчета. Обращается внимание на необходимость выделения точки отсчета
для определения таксисных отношений. Точкой отсчета при этом является первая пропозиция полипредикативного комплекса. Предлагается применять понятие зависимого и независимого таксиса только по отношению к способам выражения таксисных отношений. С семантической точки зрения все пропозиции полипредикативного комплекса представляются зависимыми от пропозиции, принятой за точку отсчета. Таксисные отношения одновременности/
предшествования/ следования дополняются еще одним отношением – последовательности,
что характерно для предложений с однородными сказуемыми и сложносочиненных предложений с поступательным развитием передаваемой ситуации. В статье подтверждаются наблюдения А.В. Бондарко, касающиеся совмещения таксиса с отношениями характеризации,
модальности, обусловленности. The article deals with certain aspects of the category of taxis on the basis of the English language.
A few schools of thought are mentioned in connection with taxis; the relation of taxis with
other temporal categories is touched upon, such as tense, aspect, and time correlation. The article
focuses on the possibility of rendering several taxis situations making up different temporal periods
within one sentence. Expansion of taxis volume is suggested through the inclusion of constructions
with object clauses in modus-dictum complexes in the narrative mode into taxis relations on the
condition that the modus tense does not coincide with the moment of speech as a starting point. The
starting point is the first proposition of a poly-predicative complex. The author suggests that the notion
of dependent and independent taxis should be used only in reference to means of expressing
taxis relations. From the semantic point of view all the propositions of a poly-predicative complex
are considered to be dependent on the proposition taken as a starting point. Taxis relations of simultaneity/
precedence/ following are enlarged by adding one more relation, that of succession, which
is characteristic of sentences with homogeneous predicates and compound sentences of a successive
development of the situation rendered. The article confirms A.V. Bondarko’s observations concerning
the combination of taxis with relations of characterization, modality, conditionality
Water Taxis in the San Francisco Bay Area: From travel time to quality time: Is there a viable service concept?
No full textThis thesis presents a discrete-choice model as the basis to forecast market shares for high-end water taxis in the San Francisco Bay Area. Waterborne mobility studies are growing in numbers, but studies towards the potential of personalized versions thereof is scarce. Three service concepts are designed as business models and compared on business potential. It is surprising to see that, compared to the very low public transit prices, this service still seems to reach market shares of 10% at ticket prices of up to $50 per single trip.Transport and Logistics' OrganisationTechnology, Policy and Managemen
THE REALIZATION OF THE QUALITY SEMANTICS IN ENGLISH (ON THE EXAMPLE OF TAXIS SEMANTICS)
No full textThe article examines the functioning of the structures containing nuclear components of autonomous taxis when realizing the function of synchronicity in English. The study is conducted by the material of modern fiction. The author analyzes literary personages’ direct speech and discovers the typical peculiarities of the taxis semantics of synchronicity realization in col- loquial speech. Then the researcher compares adults’ and children’s speech spheres and identifies similarities and differences between them
Les grands taxis et la mobilité interurbaine au Maroc. Service public, acteurs privés
No full textIn Morocco, the transportation services provided by collective taxis constitute a fundamental aspect of mobility in that country. Collective taxis interact with other means of transportation, either in competition or in complementarity . This form of transport constitutes a technical adaptation and responds to the needs of populations by compensating for certain inadequacies of Morocco's transport system. Collective taxis permit flexibility in scheduling and destinations and respond to individual needs of users. In spite of regulations at a national level, the spatial distribution and organization of this form of transport varies a good deal. Research on collective taxis also provides insight into Moroccan migration behavior and the representations that people have of their travel experiences.Au Maroc, les services de transport des taxis collectifs constituent un support original de la mobilité. Les grands taxis sont en interaction avec les autres moyens de se déplacer : situation de concurrence ou de suppléance. Ils constituent, une adaptation technique et répondent aux besoins des populations en palliant l'insuffisance de l'offre. Dans un contexte où la notion d'espace-temps se contracte, ils permettent une souplesse d'horaires et de desserte. Ils répondent à des besoins individuels d'usagers qui se déplacent collectivement. Malgré une homogénéité de la réglementation à l'échelle nationale, les grands traits de leurs fonctions, de leur distribution spatiale et de leur organisation diffèrent selon l 'espace étudié. Des recherches sur les grands taxis permettent d'étudier le système migratoire marocain et les représentations que les personnes ont de leurs vécus des déplacements. Ce mode de transport constitue un indicateur efficace pour analyser à la fois les comportements associés à la mobilité et les réseaux urbains.Le Tellier Julien. Les grands taxis et la mobilité interurbaine au Maroc. Service public, acteurs privés. In: Méditerranée, tome 100, 1-2-2003. Recherches récentes en géographie aixoise, sous la direction de Roland Courtot . pp. 53-58
Phenotypic variation and molecular signaling in the interaction of the rhizosphere bacteria Acidovorax sp. N35 and Rhizobium radiobacter F4 with roots
No full textThe aim of this doctoral thesis was to investigate the factors relevant in plant interaction of two plant growth promoting rhizobacteria (PGPR). For this, the strain Acidovorax sp. N35 isolated from surface sterilized wheat roots and the two strains F4 and F7 of Rhizobium radiobacter, a bacterium associated with the plant growth promoting fungus Piriformospora indica, were chosen. First of all, the isolate N35 was characterized using phylogenetic and taxonomic methods. The 16S rRNA gene sequence analysis showed that strain N35 has the closest sequence similarities (98.2, 98.5 and 99.0 %) to the environmental Acidovorax species A. delafieldii, A. facilis and A. defluvii. The DNA-DNA hybridization values clearly separated the isolate from these three species. Additionally, phenotypic properties, such as substrate metabolization profiles as determined by a Biolog GN2 assay and cell wall fatty acid profiles concerning the fatty acids C16:0, C16:1ω7cis/trans, C17:0cyclo and C18:0cyclo and C19:0cyclo, facilitated the differentiation of the newly isolated strain N35 from its closest relatives. Thus, the strain N35 was classified as representative of a new species within the genus Acidovorax, and the name Acidovorax radicis sp. nov. is suggested.
“Cand. A. radicis” N35 undergoes an irreversible phenotypic variation, resulting in different colony shapes on agar plate. In soil system, both phenotypes showed a plant growth promoting effect both on barley roots and shoots. The wild type N35 (rough colony type) had a better plant growth promoting effect on barley in comparison with phenotype variant N35v (smooth colony type). Wild type and phenotype variant cells of “cand. A. radicis” N35 were labeled with GFP and/or YFP and their separate and co-colonization behavior was investigated in a monoxenic system and a soil system using a CLSM for detection. Both types of N35 could endophytically colonize barley roots after 12 weeks inoculation in the soil system. Competitive root colonization behavior was observed after co-inoculation with differentially labeled wild type N35 and phenotype variant N35v bacteria, where the wild type showed dominant colonization of barley roots compared to the phenotype variant. Moreover, the variant N35v lost its motility due to missing flagella and swarming ability. The differences of both types at genetic level were investigated using whole genome sequence data obtained from 454 pyrosequencing (Roche) using the GS FLX Titanium chemistry. As only difference in the genome sequence, a 16 nucleotides deletion was identified in the mutL gene, which encodes for the mismatch repair protein MutL. In phenotype N35v, the frame shift caused by this deletion leads to the formation of a stop codon in the coding gene, resulting in a truncated MutL protein with a missing functional MutL C-terminal domain. This mutation occurred in exactly the same way in all investigated phenotype variants. These results suggest that MutL might be directly or indirectly responsible for the phenotypic variation in “cand. A. radicis” N35.
Quorum sensing signaling molecules produced by “cand. A. radicis” N35 were identified using biosensors as well as Fourier transform ion cyclotron resonance - mass spectrometry (FT-ICR-MS) and ultra performance liquid chromatography (UPLC). Both types of “cand. A. radicis” N35 possess the same AraI/AraR quorum sensing system, which belongs to the LuxI/LuxR type. The two N35 phenotypes produced nearly the same amount of 3-OH-C10-HSL in the exponential growth phase. A co-inoculation experiment of AHL producing wild type N35 and a constructed AHL negative mutant N35 ΔaraI showed that wild type N35 had a dominant colonization behavior compared to the AHL negative mutant on barley roots in a monoxenic system. These data indicate that quorum sensing is involved in regulation of root colonization by “cand. A. radicis” N35.
The second examined PGPR, R. radiobacter, which occurs naturally as endofungal bacterium in the plant growth promoting fungus P. indica, was demonstrated to colonize the surface of barley roots with fluorescence in situ hybridization (FISH) in a monoxenic system. The interaction of P. indica harboring R. radiobacter with other rhizobacteria was investigated using plate confrontation assays. Antibiotics and lipopeptides produced and excreted by the plant growth enhancing rhizobacterium Bacillus amyloliquefaciens FZB42 and the biocontrol rhizobacterium Pseudomonas fluorescens SS101 were shown to be responsible for the observed inhibition of P. indica by these bacteria. R. radiobacter F4 and F7 were able to synthesize a variety of oxo- and hydroxyl-C8- to C12-HSL compounds. In addition, both strains also produced coumaroyl-HSL when coumaric acid was supplied in the medium. The lactonase expressing transformants F4 NM13 and F7 NM13, which are the AHL negative phenotypes, abolished the lipase and siderophore activity. Considering this, quorum sensing influences the production of metabolites including lipase and siderophores in R. radiobacter F4 and F7. Further work should be directed to the question whether quorum sensing also plays a role in the interaction of the bacterium with fungus and/or plant
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