Different Means Of Transport Research Articles

Visualizing Long-Range Movement of the Morphogen Xnr2 in the Xenopus Embryo

One way in which cells acquire positional information during embryonic development is by measuring the local concentration of a signaling factor, or morphogen, that is secreted by an organizing center . The ways in which morphogen gradients are established, particularly in vertebrates, remain obscure, although various suggestions have been made for the mechanisms by which signaling molecules traverse fields of cells. These include simple diffusion, "cytonemes", filopodia, "argosomes", and "transcytosis". In this study, we use a functional EGFP-tagged ligand to visualize long-range signaling in the Xenopus embryo in real time. Our results show that the TGF-beta family member Xnr2 is secreted efficiently from embryonic cells, and a new method of tissue recombination allows us to investigate the way in which the morphogen traverses multiple cell diameters. This reveals that Xnr2 exerts long-range effects by diffusing rapidly through the extracellular milieu of nonexpressing cells. No evidence has been obtained for long-range signaling through cytonemes, filopodia, argosomes, or transcytosis. In demonstrating that long-range signaling in the early Xenopus embryo occurs by diffusion rather than by these alternative routes, our results suggest that different morphogens in different developmental contexts use different means of transport.

The role of the railway with regard to mode choice in medium range travel

This article examines Swiss people's transport means preferences in journeys over 100km. The study is based on a conditional survey research technique. When the decision criteria/ preferences are viewed from an angle that is independent of (and thus generally valid for) any choice of means of transport, the most important quality factors turn out to be safety, travelling time, punctuality, flexibility and travelling comfort. The factors “relaxation” and “(productive) use of time” are of comparatively minor importance, which can be related to the fact that travelling is seen as an end in itself. When the issue is looked at from the angle of a comparison between different means of transport, it becomes clear that there are undisputed advantages of ▪ the train over the car, particularly concerning safety with regard to accidents, relaxation and rest, a productive use of time, a minimisation of stress, and punctuality; ▪ the train over the aircraft with regard to lower overall costs, the frequency of connections, and punctuality; ▪ and the aircraft over the train with regard to travelling time. Costs only become really relevant in connection with air travel. It is interesting to note that a majority of the quality criteria which are generally considered to be the most relevant remain without any influence on the decision to choose one or the other means of transport. Indeed, there are not even any connections, overall, between people's general predispositions and their specific decisions for or against any particular means of transport in a certain situation. Only travelling time plays a central role both in the general and in the situational view.

Calculation of energy consumption and pollutant emissions on freight transport routes

An important strategy to reduce energy consumption and pollutant emissions is to displace parts of the freight traffic performance from road and air to rail and inland navigation. The calculation with average emission factors, which refer to traffic performances, promises an improvement in comparison to the status quo. If specific transports from a starting point A to a destination B are studied, some objections to using such average emission factors come to light, for example the different distances for the single means of transport, pre-trips and post-trips in the case of bi-modal traffic and different weight load factors. The results of a study, in which the energy consumption and the pollutant emissions were investigated as realistically as possible, show that the use of flat-rate average factors for the comparison of different means of transport in freight transport is not permissible. Further, they show that in regard to climate demands, it is not possible to make general recommendations for specific transport modes. For extensive calculations it is necessary to have, for all transport modes, emission factors which are based on the kilometric performance and differentiated to the vehicle type, the weight load factor, and the operating conditions. At the end of the paper the presented results of a similar study in passenger transport show the same trends.

Method for Measuring and Representing Fluctuating Noise

In the present practice of the Japanese Acoustical Society the incessantly fluctuating noise such as the city noise or that originating from the means of transportation is measured by the following method. Starting from an arbitrary point of time, instantaneous values are read at a certain time interval. Usually the reading is made every five seconds. For a noise fluctuating over a relatively narrow range, 25–30 sites are taken for measurement and for one fluctuating over a wide range, 50–100 sites. In summing up the results, the integral frequency distribution curve for the total number of measurements is plotted. The median value and the 90% range with 5% each excluded for the upper and lower limit are found. Thus the noise level can be represented by the median value and the 90% range. A similar procedure is used in the computation from the graph of a level recorder. A number of measurements are now being carried out in many cities of Japan and on different means of transportation.

Commercial Aviation and the Civil Aeronautics Act of 1938

On June 23, 1938, the Civil Aeronautics Act became law and on precedent established by the Interstate Commerce Act provided for an administrative tribunal to adjudicate disputes and protect the public interest. But more important, and in a sense differing from previous legislation related to inland transportation, the act created a quasi-judicial body empowered to formulate and administer policy for the promotion, encouragement, and expansion of a specific mode of transportation. Congressional hearings and reports on aviation, while the legislation was being considered, emphasized the intent of Congress to assign to the regulatory body the task of increasing the importance of commercial air transport; and the Civil Aeronautics Board, the body obligated to promulgate and carry-out the intent of the Act, has ever demonstrated in formal opinions an awareness of the legal responsibility of stimulating a relatively new means of transport.L The record of the past fifteen years of the air transport industry is one of phenomenal growth and vastly improved reliability. The Air Commerce Act of 1926, the Civil Aeronautics Act of 1938, the Federal Airport Act of 1946, and the marked enthusiasm of communities for contributing large sums of money for the construction and maintenance of airport facilities have provided an extremely favorable atmosphere for the expansion of air transportation. Yet, the build-up of a system such as we know today is no ordinary task and both the industry and the CAB are to be commended for the foresight and aptitude necessary to provide a new and significantly different means of transportation. But before according unqualified approbation, it is worthwhile to appraise the present system in terms of efficiency and economy, for not only will such an assessment provide an understanding and appreciation of the present system, but it will also implement an evaluation of the efficacy of the Civil Aeronautics Act as a