Mathematical retroreflectors

Retroreflectors are optical devices that reverse the direction of incident beams of light. Here we present a collection of billiard type retroreflectors consisting of four objects; three of them are asymptotically perfect retroreflectors, and the fourth one is a retroreflector which is very close to perfect. Three objects of the collection have recently been discovered and published or submitted for publication. The fourth object - notched angle - is a new one; a proof of its retroreflectivity is given.Comment: 32 pages, 19 figure

Valores como predictores de satisfacción con la vida en los jóvenes

Numa perspectiva funcionalista, os valores são uma expressão cognitiva das necessidades humanas, princípios que orientam o comportamento para metas mais pessoais, sociais ou gerais de vida, cujo impacto psicossocial merece mais investigação. Neste estudo, analisou-se em que medida o tipo de orientação dos valores prediz a satisfação com a vida de 562 jovens portugueses (n = 303, 53,9% mulheres), com idades entre 14 e 22 anos (M = 16,9, DP = 1,71), que frequentam o ensino médio: via profissionalizante (63,7%) e regular (36,3%). Os jovens completaram o Questionário de Valores Básicos e a Escala de Satisfação com a Vida. Os resultados da análise de regressão linear indicam que a orientação dos valores explica menos de um quarto da variabilidade da satisfação com a vida, o que suscita a necessidade de se analisar o seu poder explicativo em conjunto com outras variáveis, por exemplo, de personalidade e sociocognitivas.In a functionalist perspective, values are a cognitive expression of human needs as well as principles that guide behaviors to personal, social or general life goals, whose psychosocial impact deserves more investigation. This study aimed to analyze whether the type of values orientation predicts life satisfaction in 562 Portuguese youths (n = 303, 53.9% women) aged 14 to 22 years (M = 16.9; SD = 1.71), attending high school studies, being 63.7% technical and (36.3%) regular high school.Students completed the Basic Values Survey and the Satisfaction With Life Scale. The results of the linear regression analyzes indicate that the values orientation explains less than a quarter of life satisfaction variability, which indicated the need to further analyze its explanatory power together with other variables, such as, personality and socio-cognitive.Desde el punto de vista funcional, los valores son una expresión cognitiva de las necesidades humanas, principios que orientan el comportamiento hacia metas más personales, sociales o generales de vida, cuyo impacto psicosocial necesita más investigación. En este estudio se analizó en qué medida el tipo de orientación de los valores predice la satisfacción con la vida de 562 jóvenes portugueses (n = 303, 53.9% mujeres), con edades entre 14 y 22 años ( = 16.9, P = 1.71) que frecuentan Enseñanza Secundaria: profesional (63.7%) y normal (36.3%). Los jóvenes completaron el Cuestionario de Valores Básicos y la Escala de Satisfacción con la Vida. Los resultados del análisis de regresión lineal indican que la orientación de los valores explica menos de una cuarta parte de la variabilidad de satisfacción con la vida, lo que plantea la necesidad de analizar su poder explicativo, junto con otras variables, por ejemplo, de personalidad y socio-cognitivas.(undefined)info:eu-repo/semantics/publishedVersio

Spectroscopic variability of two Oe stars

The Oe stars HD45314 and HD60848 have recently been found to exhibit very different X-ray properties: whilst HD60848 has an X-ray spectrum and emission level typical of most OB stars, HD45314 features a much harder and brighter X-ray emission, making it a so-called gamma Cas analogue. Monitoring the optical spectra could provide hints towards the origin of these very different behaviours. We analyse a large set of spectroscopic observations of HD45314 and HD60848, extending over 20 years. We further attempt to fit the H-alpha line profiles of both stars with a simple model of emission line formation in a Keplerian disk. Strong variations in the strengths of the H-alpha, H-beta, and He I 5876 emission lines are observed for both stars. In the case of HD60848, we find a time lag between the variations in the equivalent widths of these lines. The emission lines are double peaked with nearly identical strengths of the violet and red peaks. The H-alpha profile of this star can be successfully reproduced by our model of a disk seen under an inclination of 30 degrees. In the case of HD45314, the emission lines are highly asymmetric and display strong line profile variations. We find a major change in behaviour between the 2002 outburst and the one observed in 2013. This concerns both the relationship between the equivalent widths of the various lines and their morphologies at maximum strength (double-peaked in 2002 versus single-peaked in 2013). Our simple disk model fails to reproduce the observed H-alpha line profiles of HD45314. Our results further support the interpretation that Oe stars do have decretion disks similar to those of Be stars. Whilst the emission lines of HD60848 are explained by a disk with a Keplerian velocity field, the disk of HD45314 seems to have a significantly more complex velocity field that could be related to the phenomenon that produces its peculiar X-ray emission.Comment: Accepted for Publication in A&

Prototype Near-Field/GIS Model for Sequestered-CO2 Risk Characterization and Management

Detecting unmapped abandoned wells thus remains a major carbon sequestration (CS) technology gap. Many (>10{sup 5}) abandoned wells are thought to lie in potential sequestration sites. For such wells, risk analysis to date has focused on aggregate long-term future impacts of seepage at rates < or << {approx}1 g m{sup 2} d{sup -1} on storage goals as sequestered plumes encroach upon wells with assumed distributions of seal ineffectiveness (Oldenburg and Unger, 2003; Saripali et al. 2003; Celia, 2005). However, unmapped abandoned wells include an unknown number without any effective seal at all, venting through which may dominate CO{sub 2}-loss scenarios. A model of such a well is Crystal Geyser (CG), a prospective oil well abandoned in the 1930s with no barrier installed after it encountered a natural CO{sub 2} reservoir rather than oil (Baer and Rigby, 1978; Rinehart, 1980). CG demonstrates how an unimpeded conduit to the surface now regularly vents from 10{sup 3} to >10{sup 4} kg of CO{sub 2} gas to the terrestrial surface (Figure 1). Unique field data recently gathered from Crystal Geyser (CG) in Utah (Gouveia et al. 2005) confirm that, although resulting surface CO{sub 2} concentrations resulting from CG-like eruptions would likely be safe in general, they could accumulate to pose lethal hazards under relatively rare meteorological and topographic (MT) conditions. This source of foreseeable risk needs to be managed if carbon sequestration is to be publicly accepted. To address this concern, we used CG field data to estimate the source term for a prototype model that identifies zones at relatively highly elevated risk for sequestered-CO{sub 2} casualties. Such a model could be applied both to design and comply with future regulatory requirements to survey high-risk zones in each proposed sequestration site for improperly sealed wells

The Concentration and Distribution of Depleted Uranium (DU) and Beryllium (Be) in Soil and Air on Illeginni Island at Kwajalein Atoll

Re-entry vehicles on missiles launched at Vandenberg Air Force base in California re-enter at the Western Test Range, the Regan Test Site (RTS) at Kwajalein Atoll. An environmental Assessment (EA) was written at the beginning of the program to assess potential impact of Depleted Uranium (DU) and Beryllium (Be), the major RV materials of interest from a health and environmental perspective. The chemical and structural form of DU and Be in RVs is such that they are insoluble in soil water and sea water. Consequently, residual concentrations of DU and Be observed in soil on the island are not expected to be toxic to plant life because there is essentially no soil to plant uptake. Similarly, due to their insolubility in sea water there is no uptake of either element by marine biota including fish, mollusks, shellfish and sea mammals. No increase in either element has been observed in sea life around Illeginni Island where deposition of DU and Be has occurred. The critical terrestrial exposure pathway for U and Be is inhalation. Concentration of both elements in air over the test period (1989 to 2006) is lower by a factor of 10,000 than the most restrictive U.S. guideline for the general public. Uranium concentrations in air are also lower by factors of 10 to 100 than concentrations of U in air in the U.S. measured by the EPA (Keith et al., 1999). U and Be concentrations in air downwind of deposition areas on Illeginni Island are essentially indistinguishable from natural background concentrations of U in air at the atolls. Thus, there are no health related issues associated with people using the island

Active Galactic Nuclei under the scrutiny of CTA

Active Galactic Nuclei (hereafter AGN) produce powerful outflows which offer excellent conditions for efficient particle acceleration in internal and external shocks, turbulence, and magnetic reconnection events. The jets as well as particle accelerating regions close to the supermassive black holes (hereafter SMBH) at the intersection of plasma inflows and outflows, can produce readily detectable very high energy gamma-ray emission. As of now, more than 45 AGN including 41 blazars and 4 radiogalaxies have been detected by the present ground-based gamma-ray telescopes, which represents more than one third of the cosmic sources detected so far in the VHE gamma-ray regime. The future Cherenkov Telescope Array (CTA) should boost the sample of AGN detected in the VHE range by about one order of magnitude, shedding new light on AGN population studies, and AGN classification and unification schemes. CTA will be a unique tool to scrutinize the extreme high-energy tail of accelerated particles in SMBH environments, to revisit the central engines and their associated relativistic jets, and to study the particle acceleration and emission mechanisms, particularly exploring the missing link between accretion physics, SMBH magnetospheres and jet formation. Monitoring of distant AGN will be an extremely rewarding observing program which will inform us about the inner workings and evolution of AGN. Furthermore these AGN are bright beacons of gamma-rays which will allow us to constrain the extragalactic infrared and optical backgrounds as well as the intergalactic magnetic field, and will enable tests of quantum gravity and other "exotic" phenomena.Comment: 28 pages, 23 figure

The Hahn Quantum Variational Calculus

We introduce the Hahn quantum variational calculus. Necessary and sufficient optimality conditions for the basic, isoperimetric, and Hahn quantum Lagrange problems, are studied. We also show the validity of Leitmann's direct method for the Hahn quantum variational calculus, and give explicit solutions to some concrete problems. To illustrate the results, we provide several examples and discuss a quantum version of the well known Ramsey model of economics.Comment: Submitted: 3/March/2010; 4th revision: 9/June/2010; accepted: 18/June/2010; for publication in Journal of Optimization Theory and Application