Corrections to the fluxes of a neutrino factory

To reach their physical goals, future neutrino factories using muon decay aim at an overall flux precision of or better. We analytically study the QED radiative corrections to the neutrino differential distributions from muon decay. Kinematic uncertainties due to the divergence of the muon beam are considered as well. The resulting corrections to the neutrino flux turn out to be of order , safely below the required precision. Received: 10 September 2002 / Revised version: 4 April 2003 / Published online: 2 June 2003 RID="a" ID="a" e-mail: alicia@delta.ft.uam.es RID="b" ID="b" e-mail: mena@delta.ft.uam.es     

Conformally flat sources for the Linet–Tian spacetime

We investigate the matching, across cylindrical surfaces, of static cylindrically symmetric conformally flat spacetimes with a cosmological constant $\Lambda $ , satisfying regularity conditions at the axis, to an exterior Linet–Tian spacetime. We prove that for $\Lambda \le 0$ such matching is impossible. On the other hand, we show through simple examples that the matching is possible for $\Lambda >0$ . We suggest a physical argument that might explain these results.     

Soil radon time series: Surveys in seismic and volcanic areas

Soil radon surveys have been performed in a long term monitoring basis with SSNTD (LR 115 type II), in order to observe possible fluctuations due to high magnitude seismic events and volcanic eruptions. Five-year radon time series are available in stations located in an intense seismic zone located along the Pacific coast of Mexico. The series analyses have been performed as a function of the local seismicity and geological characteristics. A discussion is intended to explain the lack of biunivocal relation between single radon peaks and earthquakes for the long term monitoring data using SSNTDs. Examples of short term radon anomalies obtained with continuous probes are also discussed as a function of local earthquakes and meteorological perturbations. Additionally, complementary results from recent changes in the activity pattern of an active volcano indicate that degassing process induced anomalous soil radon emanation correlated with the volcanic activity changes.     

Secondary ion yields produced by keV atomic and polyatomic ion impacts on a self-assembled monolayer surface

A suite of keV polyatomic or 'cluster' projectiles was used to bombard unoxidized and oxidized self-assembled monolayer surfaces. Negative secondary ion yields, collected at the limit of single ion impacts, were measured and compared for both molecular and fragment ions. In contrast to targets that are orders of magnitude thicker than the penetration range of the primary ions, secondary ion yields from polyatomic projectile impacts on self-assembled monolayers show little to no enhancement when compared with monatomic projectiles at the same velocity. This unusual trend is most likely due to the structural arrangement and bonding characteristics of the monolayer molecules with the Au(111). Copyright 1999 John Wiley & Sons, Ltd.     

Direct equilibration of soil water for delta(18)O analysis and its application to tracer studies

Current methods for stable oxygen isotopic (delta (18)O) analysis of soil water rely on separation of water from the soil matrix before analysis. These separation procedures are not only time consuming and require relatively large samples of soil, but also have been shown to introduce a large potential source of error. Current research at Queen's University Belfast is focused on using direct equilibration of CO(2) with the pore water to eliminate this extraction step using the automated Multiprep system and a Micromass Prism III isotope ratio mass spectrometer (IRMS). The findings of this research indicate the method is less time consuming, more reliable, and reproducible to within accepted limits (+/-0.1% per thousand delta (18)O). In this study the direct equilibration method is used to analyse delta (18)O tracer profiles in the unsaturated zone of field soils, concurrently with chloride tracer profiles, which can be used to assess infiltration rates and mechanisms through the unsaturated zone. Copyright 1999 John Wiley & Sons, Ltd.     

Volcanic monitoring for radon and chemical species in the soil and in spring water samples

Soil radon has been monitored at two fixed stations in the northern flank of Popocatepetl Volcano, a high risk volcano located 60 km SE from Mexico City. Water samples from three springs were also studied for radon as well as major and trace elements. Radon in the soil was recorded using track detectors. Radon in the water samples was evaluated using the liquid scintillation method and an Alphaguard. The major elements were determined through conventional chemical methods and trace elements using an ICP-MS equipment. Soil radon levels were low, indicating a moderate diffuse degassing through the flanks of the volcano. Groundwater radon had almost no relation with the eruptive stages. Water chemistry was stable in the reported time (2000–2002).     

Iron homeostasis in neuronal cells: a role for IREG1

Background  

Iron is necessary for neuronal function but in excess generates neurodegeneration. Although most of the components of the iron homeostasis machinery have been described in neurons, little is known about the particulars of their iron homeostasis. In this work we characterized the response of SH-SY5Y neuroblastoma cells and hippocampal neurons to a model of progressive iron accumulation.     

Constraining inverse-curvature gravity with supernovae

We show that models of generalized modified gravity, with inverse powers of the curvature, can explain the current accelerated expansion of the Universe without resorting to dark energy and without conflicting with solar system experiments. We have solved the Friedmann equations for the full dynamical range of the evolution of the Universe and performed a detailed analysis of supernovae data in the context of such models that results in an excellent fit. If we further include constraints on the current expansion of the Universe and on its age, we obtain that the matter content of the Universe is 0.07相似文献