3,196 research outputs found

    Observations of cosmic ray induced phosphenes

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    Phosphene observations by astronauts on flights near and far from earth atmosphere are discussed. It was concluded that phosphenes could be observed by the naked eye. Further investigation is proposed to determine realistic human tolerance levels for extended missions and to evaluate the need to provide special spacecraft shielding

    (1+1)-Dimensional Yang-Mills Theory Coupled to Adjoint Fermions on the Light Front

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    We consider SU(2) Yang-Mills theory in 1+1 dimensions coupled to massless adjoint fermions. With all fields in the adjoint representation the gauge group is actually SU(2)/Z_2, which possesses nontrivial topology. In particular, there are two distinct topological sectors and the physical vacuum state has a structure analogous to a \theta vacuum. We show how this feature is realized in light-front quantization, with periodicity conditions used to regulate the infrared and treating the gauge field zero mode as a dynamical quantity. We find expressions for the degenerate vacuum states and construct the analog of the \theta vacuum. We then calculate the bilinear condensate in the model. We argue that the condensate does not affect the spectrum of the theory, although it is related to the string tension that characterizes the potential between fundamental test charges when the dynamical fermions are given a mass. We also argue that this result is fundamentally different from calculations that use periodicity conditions in x^1 as an infrared regulator.Comment: 20 pages, Revte

    The Model Cities Program

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    The period from 1961 through 1965 saw a dramatic increase in the number of federal grant-in-aid programs and the total federal funding levels directed at curing the ills of the urban community. There was a persistent anxiety, however, that, despite the proliferation of new drugs administered to the patient for his array of symptoms, the progress was not satisfactory, and that time was running out. In October, 1965, a Task Force on Urban Problems was appointed by President Johnson to study urban problems and recommend action. The Task Force looked at the prior efforts and decided a new approach was necessary-a treatment to be commenced in selected cities as a demonstration. They recommended that the federal, state and local medicine men consult with each other in order to develop a program of drug therapy which would be comprehensive, and coordinated. They also recommended that massive new types and higher dosage levels of drugs were necessary if the patient was to be revitalized. The basic Task Force recommendation was accepted by the President and presented to the Congress in his message of January 26, 1966. A proposed Demonstration Cities Act of 1966 was introduced into Congress, which was later consolidated with other provisions into an omnibus bill, and finally was enacted as Title I of the Demonstration Cities and Metropolitan Development Act of 1966. As HUD commenced to implement the new program, it was given its popular name, the Model Cities Program, a designation not appearing in the Act. This article presents this, program in its historical perspective and its posture as developed administratively by the Johnson Administration. Its full potential and direction will unfold during the Nixon Administration. Secretary of Housing and Urban Development, George W. Romney, has endorsed the concept underlying the Program and announced Presidential approval of certain revisions in the administration of the Program.\u2

    Applying logic to pulmonary artery catheter use

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    Mansour and colleagues recommend not routinely using the pulmonary artery catheter to guide hemodynamic management in the intensive care unit, because the perceived benefits are largely intangible [1]. Pulmonary artery catheter monitoring of the right ventricular ejection fraction (RVef) and of the right ventricular end-diastolic volume (EDV), however, reflects powerful yet underutilized relationships that assess right ventricular performance. Since the cardiac output equals the product of the RVef, the EDV and the heart rate, one can assess the RVef to EDV relations as direct measures of right ventricular performance. A series of RVef, EDV and heart rate combinations can give the same cardiac output (Figure 1); monitoring or targeting cardiac output alone ignores this reality. For example, in hypovolemia the EDV is low and the RVef is increased

    Quantum Spectra of Triangular Billiards on the Sphere

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    We study the quantal energy spectrum of triangular billiards on a spherical surface. Group theory yields analytical results for tiling billiards while the generic case is treated numerically. We find that the statistical properties of the spectra do not follow the standard random matrix results and their peculiar behaviour can be related to the corresponding classical phase space structure.Comment: 18 pages, 5 eps figure

    Brazilian teenagers and beer advertising: relationship between exposure, positive response, and alcohol consumption

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    Brazilian teenagers report problematic patterns of alcohol consumption. Alcohol advertising strategies are one of the main factors influencing adolescents' alcohol consumption. The aim of this study was to evaluate the relationship between positive responses to TV beer commercials, exposure, and alcohol consumption. Thirty-two recent TV commercials were shown to 133 high school students from public schools in São Bernardo do Campo, São Paulo State, Brazil. The subjects recorded how well they liked the ads and how often they had already watched each commercial. The teenagers also reported their alcohol consumption rates. The ten commercials analyzed in this article were the five most popular and the five least popular. The analysis showed that subjects had already seen the five most popular ads, but not the five least popular. In addition, the five most popular ads received higher scores from teenagers that reported having consumed beer during the previous month. The study found a positive relationship between enjoying beer advertising and exposure to beer ads, as well as between alcohol consumption and positive responses to alcohol commercials.No Brasil, evidências epidemiológicas entre jovens e adolescentes indicam preocupante padrão de consumo de álcool. Entre os fatores que influenciam o consumo dos mais jovens estão as estratégias de publicidade. Pretendeu-se avaliar a relação entre apreciação das propagandas televisivas de cerveja, exposição a essas propagandas e consumo de álcool entre adolescentes. Trinta e duas propagandas recentes foram exibidas a 133 estudantes, de 1º e 2º anos do Ensino Médio de escolas públicas de São Bernardo do Campo, São Paulo, Brasil. Para cada propaganda, atribuíram notas (0 a 10) representando a apreciação e quantas vezes já tinham assistido cada uma anteriormente (exposição). Responderam se consumiam álcool e com qual freqüência. Dez das 32 propagandas foram incluídas na análise estatística (as cinco mais e as cinco menos apreciadas). As cinco propagandas mais apreciadas já tinham sido assistidas anteriormente, o que não ocorreu com as menos pontuadas. Ademais, entre as cinco mais apreciadas, notas estatisticamente maiores foram atribuídas pelos adolescentes que consumiram cerveja no último mês. O estudo encontrou uma relação positiva entre apreciação e exposição, bem como com o consumo de álcool.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Universidade Federal de São Paulo (UNIFESP) Departamento de PsiquiatriaUniversidade Federal de São Paulo (UNIFESP) Departamento de Medicina PreventivaUNIFESP, Depto. de PsiquiatriaUNIFESP, Depto. de Medicina PreventivaSciEL

    Modal expansions and non-perturbative quantum field theory in Minkowski space

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    We introduce a spectral approach to non-perturbative field theory within the periodic field formalism. As an example we calculate the real and imaginary parts of the propagator in 1+1 dimensional phi^4 theory, identifying both one-particle and multi-particle contributions. We discuss the computational limits of existing diagonalization algorithms and suggest new quasi-sparse eigenvector methods to handle very large Fock spaces and higher dimensional field theories.Comment: new material added, 12 pages, 6 figure

    Vacuum Structure of Two-Dimensional Gauge Theories on the Light Front

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    We discuss the problem of vacuum structure in light-front field theory in the context of (1+1)-dimensional gauge theories. We begin by reviewing the known light-front solution of the Schwinger model, highlighting the issues that are relevant for reproducing the θ\theta-structure of the vacuum. The most important of these are the need to introduce degrees of freedom initialized on two different null planes, the proper incorporation of gauge field zero modes when periodicity conditions are used to regulate the infrared, and the importance of carefully regulating singular operator products in a gauge-invariant way. We then consider SU(2) Yang-Mills theory in 1+1 dimensions coupled to massless adjoint fermions. With all fields in the adjoint representation the gauge group is actually SU(2)/Z2/Z_2, which possesses nontrivial topology. In particular, there are two topological sectors and the physical vacuum state has a structure analogous to a θ\theta vacuum. We formulate the model using periodicity conditions in x±x^\pm for infrared regulation, and consider a solution in which the gauge field zero mode is treated as a constrained operator. We obtain the expected Z2Z_2 vacuum structure, and verify that the discrete vacuum angle which enters has no effect on the spectrum of the theory. We then calculate the chiral condensate, which is sensitive to the vacuum structure. The result is nonzero, but inversely proportional to the periodicity length, a situation which is familiar from the Schwinger model. The origin of this behavior is discussed.Comment: 29 pages, uses RevTeX. Improved discussion of the physical subspace generally and the vacuum states in particular. Basic conclusions are unchanged, but some specific results are modifie
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