New Symmetries of Massless QED

An infinite number of physically nontrivial symmetries are found for abelian gauge theories with massless charged particles. They are generated by large $U(1)$ gauge transformations that asymptotically approach an arbitrary function $\varepsilon(z,\bar{z})$ on the conformal sphere at future null infinity ($\mathscr I^+$) but are independent of the retarded time. The value of $\varepsilon$ at past null infinity ($\mathscr I^-$) is determined from that on $\mathscr I^+$ by the condition that it take the same value at either end of any light ray crossing Minkowski space. The $\varepsilon\neq$ constant symmetries are spontaneously broken in the usual vacuum. The associated Goldstone modes are zero-momentum photons and comprise a $U(1)$ boson living on the conformal sphere. The Ward identity associated with this asymptotic symmetry is shown to be the abelian soft photon theorem.Comment: 17 pages, v2: typos in equations correcte

Application of ERTS-1 imagery to the harvest model of the US Menhaden fishery

Preliminary results of an experiment to demonstrate the utility of ERTS-1 imagery for providing significant information to the harvest model of the menhaden industry are reported. Fisheries and related environmental data were obtained discontinuously throughout the 1973 menhaden (a surface schooling, coastal species) fishing season in Mississippi Sound. The unexpected complexity of the physical environment in Mississippi Sound precluded simplistic analysis of fish/environment relationships. Preliminary indications are that an association does exist between fish availability and differences in water transparency (turbidity) within the Sound. A clearer relationship is developing between major turbid features, imaged by ERTS-1 and location of successful fishing attempts. On all occasions where relatively cloudfree ERTS-1 overflight days coincided with fishery activity, overlays of catch location of ERTS-1 images show an association of school position with interfaces between imaged turbid features. Analysis is currently underway to determine persistence of such associations in an attempt to define minimum satellite return time necessary to maintain continuity of associations

The war on cancer: failure of therapy and research

A generally-held beliefby both the medical profession and the lay public is that therapeutic medicine greatly affects health. Providing more hospital beds, doctors and resources is viewed as the path to improve health. Therapeutic medicine is of much benefit to sick people. However, with the exception of several highly contagious infections, it has not reduced the incidence of disease. This generalization applies particularly to cancer. Despite this fact most ofthe expense and effort devoted to the management of cancer is directed towards early diagnosis (screening) and improved therapy. Evidence has steadily accrued that this strategy is essentially a failure: little impact has been made on the toll taken by the major cancers. The failure of therapy, coupled with the realization that the overwhelming majority of cancer is related to environmental, particularly lifestyle, factors, dictates that prevention should be our foremost aim. It follows, therefore, that cancer research should concentrate on those environmental factors which may cause or prevent cancer. Instead, most research looks at either the detailed mechanisms of cancer formation or else investigates new types of therapy. Medicine should admit its severe limitations in therapy and redirect itself. Using the fruits of an expanded research programme into such areas as diet and exercise, medicine should strive to apply this knowledge to cancer prevention

Towards a new system of health: the challenge of western disease

Over the last three decades, the concept of Western disease has become well established. Medicine has approached this group of diseases by searching for new cures but has achieved relatively little success. We argue that medicine should now accept the failure of this strategy and place a major emphasis on prevention. The key objective is to change the climate of opinion so that prevention is taken seriously by the general population. The chief activity should be a wide ranging public education campaign so as to persuade people to live a healthier lifestyle. Medicine will require restructuring in order to carry out this work. Medical education needs to be reformed so that medical students receive the necessary training. This must be done as part of an integrated approach in which government, industry and medical research all play a major role. Governments should use taxation and subsidies in areas such as food and tobacco so as to shift consumption patterns towards healthier products. Governments must also tighten laws on tobacco sales and advertising, support health education, and improve food labelling. Industry must be made far more responsive to the health needs of the population. This should be done both by public education, so as to alter demand, and by government action. Medical research should change its emphasis from studying the detailed mechanisms of disease ("complex research") to studying the role of lifestyle factors ("simple research")

Improved aperture for modulation transfer function measurement of detector arrays beyond the Nyquist frequency

The design of an aperture for the generation of laser speckle with a flat power spectrum covering a wide band of the measurement spatial-frequency range is presented. This aperture allows for the measurement of modulation transfer function (MTF) from zero to twice the Nyquist frequency of a two-dimensional detector array. This design mitigates many of the measurement problems inherent in other aperture designs. The MTF measurement of a CCD detector array is used to demonstrate the measurement technique and illustrate the advantages of the new aperture design

Experimental modelling of lipping in insulated rail joints and investigation of rail head material improvements

An insulated rail joint is a component used to join two abutting rails whilst keeping them electrically separated from one another. This allows for the construction of track circuits and train detection within signalling systems. Electrical failure of the joints can be caused by plastic flow of the rail steel over the insulating gap, known as lipping. In the following paper this failure mode has been experimentally modelled using twin disc testing and indicative conclusions have been formed. It has been found in this testing that endpost thickness does not have an effect on the rate of lipping, but the endpost and rail material do. An endpost with higher compressive strength will perform better while tougher / harder rail steel will also improve performance. The application of a laser clad layer of tougher material on the running surface, however, gave the greatest resistance to lipping

Modelling and validation of synthesis of poly lactic acid using an alternative energy source through a continuous reactive extrusion process

PLA is one of the most promising bio-compostable and bio-degradable thermoplastic polymers made from renewable sources. PLA is generally produced by ring opening polymerization (ROP) of lactide using the metallic/bimetallic catalyst (Sn, Zn, and Al) or other organic catalysts in a suitable solvent. In this work, reactive extrusion experiments using stannous octoate Sn(Oct)2 and tri-phenyl phosphine (PPh)3 were considered to perform ROP of lactide. Ultrasound energy source was used for activating and/or boosting the polymerization as an alternative energy (AE) source. Ludovic® software, designed for simulation of the extrusion process, had to be modified in order to simulate the reactive extrusion of lactide and for the application of an AE source in an extruder. A mathematical model for the ROP of lactide reaction was developed to estimate the kinetics of the polymerization process. The isothermal curves generated through this model were then used by Ludovic software to simulate the “reactive” extrusion process of ROP of lactide. Results from the experiments and simulations were compared to validate the simulation methodology. It was observed that the application of an AE source boosts the polymerization of lactide monomers. However, it was also observed that the predicted residence time was shorter than the experimental one. There is potentially a case for reducing the residence time distribution (RTD) in Ludovic® due to the ‘liquid’ monomer flow in the extruder. Although this change in parameters resulted in validation of the simulation, it was concluded that further research is needed to validate this assumption

Innovations agro écologiques en Martinique : freins et leviers organisationnels techniques et économiques

Les résultats montrent tout d'abord que la filière de produits dits « biologiques » se structure en deux organisations de producteurs qui se différencient, tant par le mode de certification choisie que par leur niveaux d'insertion dans les dispositifs institutionnels conventionnels. Dans les deux cas néanmoins, un frein important est l'absence de maîtrise d'indicateurs sur les conditions d'évaluation économique et financière des produits biologiques. Par ailleurs, trois freins majeurs sont mis en évidence par l'analyse technico-économique et agronomique des exploitations (i) l'absence de référentiels et d'appui technique adaptés aux conditions locales, (ii) la faiblesse et la dispersion concernant l'approvisionnement et l'accès aux intrants adaptés et enfin (iii) la faible productivité du travail. Une action collective de coordination impliquant les collectivités locales, les organisations de producteurs, les organismes techniques et la recherche est nécessaire

Segmenter les paysages de l'eau : une méthode pour l'interprétation hydrodynamique des paysages (dorsale tunisienne)

International audienceThe problem of water appears to be the critical path in the analysis of Mediterranean landscapes, especially in Tunisia, where such regions are developed so as to assure better control of water. This study focused on two small watersheds belonging to a network of watersheds defined and followed by the IRD-Tunis within the framework of the AMBRE program. The importance and complementarity between photo-interpretation and ground techniques are emphasized in this work. This article offers answers to certain questions concerning landscape matters by approaching them from the “Science of the landscape” point of view, here meaning the hydrodynamic segmentation of the landscape. The study aims at delimiting and better understanding the organization of landscapes in segments and their hydrodynamic behaviour at the level of the watersheds, as well as the global impact of development on these surroundings. We ask how the landscapes are organized, what their hydrodynamic behaviours are, the impact of development in these Mediterranean surroundings and whether the notion of landscape segmentation, derived from the method of “Science of the landscape,” is pertinent to furthering the understanding of these landscape dynamics.Le problème de l'eau apparaît comme le fil conducteur essentiel de l'analyse des paysages méditerranéens, particulièrement en Tunisie où ces milieux sont entièrement aménagés dans le sens d'une plus grande maîtrise de l'eau. Cette étude a été réalisée sur deux petits bassins-versants situés dans la Dorsale tunisienne, qui font partie d'un réseau de bassins-versants défini et suivi par l'Institut de recherche pour le développement (IRD)-Tunis dans le cadre du programme AMBRE. L'accent est mis sur l'importance et la complémentarité des techniques de photo-interprétation et de terrain. Cet article cherche à apporter des réponses aux questionnements paysagers abordés sous l'angle de la « Science du paysage » – appliquée ici à la segmentation hydrodynamique des paysages. Cette recherche vise à mieux cerner et comprendre l'organisation des paysages en segments, leurs comportements hydrodynamiques à l'échelle du bassin-versant, ainsi que l'impact global des aménagements sur ces milieux. Comment s'organisent les paysages ? Quels sont les comportements hydrodynamiques de ces derniers ? Quel est l'impact de tous les aménagements réalisés dans ces milieux méditerranéens ? La notion de segmentation du paysage, extraite de la méthode de la « Science du paysage » est-elle pertinente dans la compréhension de ces dynamiques paysagères