2,171 research outputs found

    Emission of gamma rays shifted from resonant absorption by electron-nuclear double transitions in ^{151}Eu^{2+}:CaF_2

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    We show that the emission of a gamma-ray photon by a nucleus can be influenced by a microwave magnetic field acting on the atomic electrons. We study theoretically these electron-nuclear double transitions (ENDTs) for ^{151}Eu nuclei in a CaF_2 lattice at low temperature, in the presence of a static magnetic field and of a microwave magnetic field. The ENDTs acquire a significant intensity for certain resonance frequencies. The ENDTs are of interest for the identification of the position of the lines in complex M\"{o}ssbauer spectra.Comment: 8 pages; 3 Postscript figures: Fig. 1, Fig. 2(a), Fig. 2(b

    Solar electric propulsion for Mars transport vehicles

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    Solar electric propulsion (SEP) is an alternative to chemical and nuclear powered propulsion systems for both piloted and unpiloted Mars transport vehicles. Photovoltaic solar cell and array technologies were evaluated as components of SEP power systems. Of the systems considered, the SEP power system composed of multijunction solar cells in an ENTECH domed fresnel concentrator array had the least array mass and area. Trip times to Mars optimized for minimum propellant mass were calculated. Additionally, a preliminary vehicle concept was designed

    Outer jet X-ray and radio emission in R Aquarii: 1999.8 to 2004.0

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    Chandra and VLA observations of the symbiotic star R Aqr in 2004 reveal significant changes over the three to four year interval between these observations and previous observations taken with the VLA in 1999 and with Chandra in 2000. This paper reports on the evolution of the outer thermal X-ray lobe-jets and radio jets. The emission from the outer X-ray lobe-jets lies farther away from the central binary than the outer radio jets, and comes from material interpreted as being shock heated to ~10^6 K, a likely result of collision between high speed material ejected from the central binary and regions of enhanced gas density. Between 2000 and 2004, the Northeast (NE) outer X-ray lobe-jet moved out away from the central binary, with an apparent projected motion of ~580 km s^-1. The Southwest (SW) outer X-ray lobe-jet almost disappeared between 2000 and 2004, presumably due to adiabatic expansion and cooling. The NE radio bright spot also moved away from the central binary between 2000 and 2004, but with a smaller apparent velocity than of the NE X-ray bright spot. The SW outer lobe-jet was not detected in the radio in either 1999 or 2004. The density and mass of the X-ray emitting material is estimated. Cooling times, shock speeds, pressure and confinement are discussed.Comment: 23 pages, 8 figure

    Hadamard states from null infinity

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    Free field theories on a four dimensional, globally hyperbolic spacetime, whose dynamics is ruled by a Green hyperbolic partial differential operator, can be quantized following the algebraic approach. It consists of a two-step procedure: In the first part one identifies the observables of the underlying physical system collecting them in a *-algebra which encodes their relational and structural properties. In the second step one must identify a quantum state, that is a positive, normalized linear functional on the *-algebra out of which one recovers the interpretation proper of quantum mechanical theories via the so-called Gelfand-Naimark-Segal theorem. In between the plethora of possible states, only few of them are considered physically acceptable and they are all characterized by the so-called Hadamard condition, a constraint on the singular structure of the associated two-point function. Goal of this paper is to outline a construction scheme for these states which can be applied whenever the underlying background possesses a null (conformal) boundary. We discuss in particular the examples of a real, massless conformally coupled scalar field and of linearized gravity on a globally hyperbolic and asymptotically flat spacetime.Comment: 23 pages, submitted to the Proceedings of the conference "Quantum Mathematical Physics", held in Regensburg from the 29th of September to the 02nd of October 201

    Production and characterization of monoclonal antibodies raised against recombinant human granzymes A and B and showing cross reactions with the natural proteins

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    The human serine proteases granzymes A and B are expressed in cytotoplasmic granules of activated cytotoxic T lymphocytes and natural killer cells. Recombinant granzyme A and granzyme B proteins were produced in bacteria, purified and then used to raise specific mouse monoclonal antibodies. Seven monoclonal antibodies (mAb) were raised against granzyme A, which all recognized the same or overlapping epitopes. They reacted specifically in an immunoblot of interleukin-2 (IL-2) stimulated PBMNC with a disulfide-linked homodimer of 43 kDa consisting of 28 kDa subunits. Seven mAb against granzyme B were obtained, which could be divided into two groups, each recognizing a different epitope. On an immunoblot, all mAb reacted with a monomer of 33 kDa protein. By immunohistochemistry, these mAb could be used to detect granzymes A and B expression in activated CTL and NK cells. The availability of these mAb may facilitate studies on the role of human cytotoxic cells in various immune reactions and may contribute to a better understanding of the role of granzmes A and B in the cytotoxic response in vivo

    Integer Vector Addition Systems with States

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    This paper studies reachability, coverability and inclusion problems for Integer Vector Addition Systems with States (ZVASS) and extensions and restrictions thereof. A ZVASS comprises a finite-state controller with a finite number of counters ranging over the integers. Although it is folklore that reachability in ZVASS is NP-complete, it turns out that despite their naturalness, from a complexity point of view this class has received little attention in the literature. We fill this gap by providing an in-depth analysis of the computational complexity of the aforementioned decision problems. Most interestingly, it turns out that while the addition of reset operations to ordinary VASS leads to undecidability and Ackermann-hardness of reachability and coverability, respectively, they can be added to ZVASS while retaining NP-completness of both coverability and reachability.Comment: 17 pages, 2 figure

    Effective quantum gravity observables and locally covariant QFT

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    Perturbative algebraic quantum field theory (pAQFT) is a mathematically rigorous framework that allows to construct models of quantum field theories on a general class of Lorentzian manifolds. Recently this idea has been applied also to perturbative quantum gravity, treated as an effective theory. The difficulty was to find the right notion of observables that would in an appropriate sense be diffeomorphism invariant. In this article I will outline a general framework that allows to quantize theories with local symmetries (this includes infinitesimal diffeomorphism transformations) with the use of the BV (Batalin-Vilkovisky) formalism. This approach has been successfully applied to effective quantum gravity in a recent paper by R. Brunetti, K. Fredenhagen and myself. In the same paper we also proved perturbative background independence of the quantized theory, which is going to be discussed in the present work as well.Comment: 16 pages, based on a plenary talk given at the 14th Marcel Grossmann Meeting in Rome (July 2015

    HV 11423: The Coolest Supergiant in the SMC

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    We call attention to the fact that one of the brightest red supergiants in the SMC has recently changed its spectral type from K0-1 I (December 2004) to M4 I (December 2005) and back to K0-1 I (September 2006). An archival spectrum from the Very Large Telescope reveals that the star was even cooler (M4.5-M5 I) in December 2001. By contrast, the star was observed to be an M0 I in both October 1978 and October 1979. The M4-5 I spectral types is by far the latest type seen for an SMC supergiant, and its temperature in that state places it well beyond the Hayashi limit into a region of the H-R diagram where the star should not be in hydrostatic equilibrium. The star is variable by nearly 2 mag in V, but essentially constant in K. Our modeling of its spectral energy distribution shows that the visual extinction has varied during this time, but that the star has remained essentially constant in bolometric luminosity. We suggest that the star is currently undergoing a period of intense instability, with its effective temperature changing from 4300 K to 3300 K on the time-scale of months. It has one of the highest 12-micron fluxes of any RSG in the SMC, and we suggest that the variability at V is due primarily to changes in effective temperature, and secondly, due to changes in the local extinction due to creation and dissipation of circumstellar dust. We speculate that the star may be nearing the end of its life.Comment: Accepted by the Astrophysical Journa

    A pilot study to evaluate the effects of C1 esterase inhibitor on the toxicity of high-dose interleukin 2.

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    In a pilot study six patients received 4 days' treatment with interleukin 2 (IL-2) [cumulative dose (CD) 264 +/- 26 x 10(6) IU m-2] and C1 esterase inhibitor (C1-INH) (loading dose 2,000 U, followed by 500-1,000 U twice daily). Toxicity was compared with that in patients given 4 days' treatment with standard (CD 66 +/- 12 x 10(6) IU m-2) or escalating-dose (CD 99 +/- 8 x 10(6) IU m-2) IL-2. IL-2-induced hypotension was equivalent and complement activation was less after IL-2 + C1-INH (C3a = 10.5 +/- 3.2 nmol l-1) than following standard (14.1 +/- 8.4 nmol l-1) or escalating-dose (18.3 +/- 2.9 nmol l-1) IL-2. This study demonstrates that C1-INH administration during IL-2 treatment is safe and warrants further study to evaluate its ability to ameliorate IL-2-induced toxicity

    Aptitud forrajera de hojas de mandioca (Manihot esculenta) y su aporte nutricional a microsilos de caña de azúcar

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    The objective of this research was to evaluate the forage productivity of different cassava cultivars and their nutritional contribution to sugarcane microsilages. For this, an essay was carried out in Corrientes, Argentina, on seven cultivars (Amarilla, Palomita, Tapó Joá, Rocha, Clon 60, Clon 30, EC-9). The characterization of the materials was carried out through the measurement of different foliar variables: foliar retention, dry leaf biomass, dry matter (DM), nitrogen (N), gross protein (PB), phosphorus (P), and potassium (K) foliar percentage. The cultivar Amarilla was highlighted for its forage production that reached 23.160 kg/DM but presented only 4.62% PB. Another five cultivars showed lower leaf productivity but protein concentration higher than 11%. About nutritional characteristics of microsilages, the treatment consisted of combining two proportions of cassava foliage and sugarcane T1 (30% cassava + 70% sugarcane) and T2 (15% cassava + 85% sugarcane). For each treatment six sampling units were made, from which three were evaluated at 30 days of silage and the remaining at 60 days. In microsilages samples were evaluated pH, %MS, N, PB, neutral (NDF) and acid detergent fiber (ADF) in each instance. In T1 pH stabilized at 60 days and in T2 at 30 days. The PB (%) was significantly higher in T1 at both times. The ADF and NDF (%) were established over time. Cassava leaves proved to be a valuable protein resource, which can be successfully ensiled to supplement nutritional deficiencies of cattle from Northeastern Argentina.El objetivo de este trabajo fue evaluar la aptitud forrajera de hojas de diferentes cultivares de mandioca y el aporte nutricional a microsilos de caña de azúcar. Los ensayos se efectuaron en Corrientes, Argentina y consistieron en dos experimentos. El primero indagó la productividad y calidad forrajera de hojas de mandioca, para lo cual se caracterizaron siete cultivares (Amarilla, Palomita, Tapó Joá, Rocha, Clon 60, Clon 30 y EC-9) a través de la medición de las variables: retención foliar, biomasa seca, porcentaje de materia seca (MS), de nitrógeno (N), proteína bruta (PB), fósforo (P) y potasio foliar (K). El cultivar Amarilla se destacó por su producción forrajera, la cual alcanzó 23.160 kg de MS/ha, pero presentó sólo 4,62% de PB. Otros cinco cultivares, presentaron menor productividad foliar pero mayor concentración proteica, superior al 11%. El segundo experimento investigó las características nutricionales de microsilos al evaluar dos tratamientos que consistieron en combinar dos proporciones de follaje de mandioca y caña de azúcar: T1 (30% mandioca + 70% caña) y T2 (15% mandioca + 85% caña). En cada tratamiento se hicieron seis unidades de muestreo, de las cuales tres fueron evaluadas a los 30 días y las restantes a los 60 días de ensilado (dde), determinándose en cada instancia: pH, %MS, N, PB, fibra detergente neutra (FDN) y fibra detergente ácida (FDA). En T1 el pH se estabilizó a los 60 dde y en T2 a los 30 dde. La PB (%) fue significativamente superior en T1 en ambos momentos. Los % de FDA y FDN fueron estables en el tiempo. Las hojas de mandioca demostraron ser un valioso recurso proteico, que puede ensilarse exitosamente para suplementar deficiencias nutricionales de la ganadería del nordeste argentino
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