CU Virginis - The First Stellar Pulsar

CU Virginis is one of the brightest radio emitting members of the magnetic chemically peculiar (MCP) stars and also one of the fastest rotating. We have now discovered that CU Vir is unique among stellar radio sources in generating a persistent, highly collimated, beam of coherent, 100% polarised, radiation from one of its magnetic poles that sweeps across the Earth every time the star rotates. This makes the star strikingly similar to a pulsar. This similarity is further strengthened by the observation that the rotating period of the star is lengthening at a phenomenal rate (significantly faster than any other astrophysical source - including pulsars) due to a braking mechanism related to its very strong magnetic field.Comment: 10 pages including 2 figure

The Chandrayaan-1 X-ray spectrometer

The Chandrayaan-1 X-ray Spectrometer (C1XS) is a compact X-ray spectrometer for the Chandrayaan-1 lunar mission. It exploits heritage from the D-C1XS instrument on ESA’s SMART-1 mission. C1XS is designed to measure absolute and relative abundances of major rock-forming elements (principally Mg, Al, Si, Ti, Ca and Fe) over the lunar surface. The baseline design consists of 24 nadir pointing Swept Charge Device detectors, which provide high detection efficiency in the 1–7 keV range, which contains the X-ray fluorescence lines of the above elements of interest. Micromachined collimators provide a 14 degree FWHM FOV, equivalent to 25 km from 100 km altitude. A deployable door protects the instrument during launch and cruise, and also provides a 55Fe calibration X-ray source for detector calibration. Additional refinements compared to D-C1XS will result in a significantly improved energy resolution. To record the incident solar X-ray flux at the Moon, C1XS carries an X-ray Solar Monitor (XSM). C1XS will arrive at the Moon in the run up to the maximum of the solar cycle 24, and the expected high incident X-ray flux coupled to a 100 km circular polar orbit, will provide composition data accurate to better than 10% of major elemental abundances over the lunar surface

Results from the CERN pilot CLOUD experiment

During a 4-week run in October–November 2006, a pilot experiment was performed at the CERN Proton Synchrotron in preparation for the Cosmics Leaving OUtdoor Droplets (CLOUD) experiment, whose aim is to study the possible influence of cosmic rays on clouds. The purpose of the pilot experiment was firstly to carry out exploratory measurements of the effect of ionising particle radiation on aerosol formation from trace H2SO4 vapour and secondly to provide technical input for the CLOUD design. A total of 44 nucleation bursts were produced and recorded, with formation rates of particles above the 3 nm detection threshold of between 0.1 and 100 cm -3 s -1, and growth rates between 2 and 37 nm h -1. The corresponding H2O concentrations were typically around 106 cm -3 or less. The experimentally-measured formation rates and htwosofour concentrations are comparable to those found in the atmosphere, supporting the idea that sulphuric acid is involved in the nucleation of atmospheric aerosols. However, sulphuric acid alone is not able to explain the observed rapid growth rates, which suggests the presence of additional trace vapours in the aerosol chamber, whose identity is unknown. By analysing the charged fraction, a few of the aerosol bursts appear to have a contribution from ion-induced nucleation and ion-ion recombination to form neutral clusters. Some indications were also found for the accelerator beam timing and intensity to influence the aerosol particle formation rate at the highest experimental SO2 concentrations of 6 ppb, although none was found at lower concentrations. Overall, the exploratory measurements provide suggestive evidence for ion-induced nucleation or ion-ion recombination as sources of aerosol particles. However in order to quantify the conditions under which ion processes become significant, improvements are needed in controlling the experimental variables and in the reproducibility of the experiments. Finally, concerning technical aspects, the most important lessons for the CLOUD design include the stringent requirement of internal cleanliness of the aerosol chamber, as well as maintenance of extremely stable temperatures (variations below 0.1 °C

Cellular Prion Protein Expression Is Not Regulated by the Alzheimer's Amyloid Precursor Protein Intracellular Domain

There is increasing evidence of molecular and cellular links between Alzheimer's disease (AD) and prion diseases. The cellular prion protein, PrPC, modulates the post-translational processing of the AD amyloid precursor protein (APP), through its inhibition of the β-secretase BACE1, and oligomers of amyloid-β bind to PrPC which may mediate amyloid-β neurotoxicity. In addition, the APP intracellular domain (AICD), which acts as a transcriptional regulator, has been reported to control the expression of PrPC. Through the use of transgenic mice, cell culture models and manipulation of APP expression and processing, this study aimed to clarify the role of AICD in regulating PrPC. Over-expression of the three major isoforms of human APP (APP695, APP751 and APP770) in cultured neuronal and non-neuronal cells had no effect on the level of endogenous PrPC. Furthermore, analysis of brain tissue from transgenic mice over-expressing either wild type or familial AD associated mutant human APP revealed unaltered PrPC levels. Knockdown of endogenous APP expression in cells by siRNA or inhibition of γ-secretase activity also had no effect on PrPC levels. Overall, we did not detect any significant difference in the expression of PrPC in any of the cell or animal-based paradigms considered, indicating that the control of cellular PrPC levels by AICD is not as straightforward as previously suggested

Late Cretaceous–earliest Paleogene deformation in the Longmen Shan fold-and-thrust belt, eastern Tibetan Plateau margin: pre-Cenozoic thickened crust?

This study presents structural and 40Ar/39Ar geochronological data from the southern part of the Longmen Shan fold-and-thrust belt that forms the eastern margin of the Tibetan Plateau. Investigations focused on hinterland ductile top-to-the-WNW shear deformation, which has been linked previously to late Cenozoic lower crustal flow. Consistent with previous studies, the sense of deformation is mapped as top-to-the-WNW in the Longmen Shan hinterland. The timing of the deformation is constrained by 40Ar/39Ar geochronological data of recrystallized minerals aligned along the shear foliation as Late Cretaceous–earliest Paleogene, thus predating the inferred late Cenozoic crustal flow. This deformation is contemporaneous with SE verging thrusting and loading along the Longmen Shan front, which formed a coeval ~2–3 km thick foredeep sequence along the southwestern margin of the Sichuan Basin. In the context of the regional geology, this tectonic configuration could result from either extrusion of a crustal wedge or back thrust in a duplex. Compared to other orogens, where similar crustal configurations have been reported, it is speculated that the eastern Tibetan Plateau margin acquired thickened crust and highly elevated topography in Late Cretaceous–earliest Paleogene time

RE 0044+09: A new K dwarf rapid rotator with a white dwarf companion?

We report the discovery of a new K dwarf rapid rotator with a potential white dwarf companion. The white dwarf accounts for over 90% of the observed extreme ultraviolet flux detected from this system. Analysis of ROSAT Wide Field Camera (WFC) and IUE data both suggest a white dwarf temperature of approximately 28,700 K. Optical photometry and the IUE long wavelength prime (LWP) spectrum (with the white dwarf contribution removed) imply that the late-type star has a spectral type of K1-3 V, and a distance of 55 +/- 5 pc. Using this distance, the observed IUE SWP flux, and the best-fit temperature results in a white dwarf radius of 0.0088 solar radius. The estimated white dwarf mass is then approximately 0.91 solar mass; somewhat over-massive compared to field white dwarfs. Optical photometry of the K star reveals a 'spot' modulation period of approximately 10 hr (now observed over 3 yr). However, radial velocity observations have revealed no significant variations. Spectroscopic observations place a low limit on the lithium abundance, but do show rapid rotation with a v sin i of 90 +/- 10 km/s. The K star was detected as a radio source at 3.6 cm (on two occasions) and 6 cm by the Very Large Array (VLA). The most likely evolutionary scenario is that the K star and hot white dwarf from either a wide binary or common proper motion pair with an age of 0.1-0.1 Gyr-consistent with the evolutionary timescale of the white dwarf and the rapid rotation of the K star. However, from the proper motion of the K star, this system does not seem to be associated with any of the known young stellar groups

SMART-1 highlights and relevant studies on early bombardment and geological processes on rocky planets

We present results from SMART-1 science and technology payload, in the context of the Nobel symposium on 'Physics of Planetary Systems'. SMART-1 is Europe' first lunar mission (Foing et al 2000 LPSC XXXI Abstract #1677 (CDROM); Foing et al 2001 Earth, Moon Planets 85-86 523-31; Marini et al 2002 Adv. Space Res. 30 1895-900; Racca et al 2001 Earth Moon Planets 85-86 379-95, Racca et al 2002 Planet Space Sci. 50 1323-37) demonstrating technologies for future science and exploration missions, and providing advances in our understanding of lunar origin and evolution, and general planetary questions. The mission also contributes a step in developing an international program of lunar exploration. The spacecraft, launched on 27 September 2003 as an Ariane 5 Auxiliary passenger to geostationary transfer orbit (GTO), performed a 14-month long cruise using a tiny thrust of electric propulsion alone, reached lunar capture in November 2004, and lunar science orbit in March 2005. SMART-1 carried 7 hardware experiments (Foing et al 2003 Adv. Space Res. 31 2323, Foing et al 2005 LPI/LPSC XXXVI 2404 (CDROM)) performing 10 investigations, including 3 remote-sensing instruments, used during the cruise, the mission' nominal six-months and one-year extension in lunar science orbit. Three remote sensing instruments, D-CIXS, SIR and AMIE, have returned data that are relevant to a broad range of lunar studies. The mission provided regional and global x-ray measurements of the Moon, global high-spectral resolution NIR spectrometry, high spatial resolution colour imaging of selected regions. The South Pole-Aitken Basin (SPA) and other impact basins have been prime targets for studies using the SMART-1 suite of instruments. Combined, these should aid a large number of science studies, from bulk crustal composition and theories of lunar origin/evolution, the global and local crustal composition, to the search for cold traps at the lunar poles and the mapping of potential lunar resources. We present here SMART-1 results relevant to the study of the early bombardment and geological processes on rocky planets. Further information and updates on the SMART-1 mission can be found on the ESA Science and Technology web pages, at: http://sci.esa.int/smart-1/. © 2008 The Royal Swedish Academy of Sciences.link_to_subscribed_fulltex