Comparison of continuous in situ CO2 observations at Jungfraujoch using two different measurement techniques

Since 2004, atmospheric carbon dioxide (CO2) is being measured at the High Altitude Research Station Jungfraujoch by the division of Climate and Environmental Physics at the University of Bern (KUP) using a nondispersive infrared gas analyzer (NDIR) in combination with a paramagnetic O2 analyzer. In January 2010, CO2 measurements based on cavity ring-down spectroscopy (CRDS) as part of the Swiss National Air Pollution Monitoring Network were added by the Swiss Federal Laboratories for Materials Science and Technology (Empa). To ensure a smooth transition – a prerequisite when merging two data sets, e.g., for trend determinations – the two measurement systems run in parallel for several years. Such a long-term intercomparison also allows the identification of potential offsets between the two data sets and the collection of information about the compatibility of the two systems on different time scales. A good agreement of the seasonality, short-term variations and, to a lesser extent mainly due to the short common period, trend calculations is observed. However, the comparison reveals some issues related to the stability of the calibration gases of the KUP system and their assigned CO2 mole fraction. It is possible to adapt an improved calibration strategy based on standard gas determinations, which leads to better agreement between the two data sets. By excluding periods with technical problems and bad calibration gas cylinders, the average hourly difference (CRDS – NDIR) of the two systems is −0.03 ppm ± 0.25 ppm. Although the difference of the two data sets is in line with the compatibility goal of ±0.1 ppm of the World Meteorological Organization (WMO), the standard deviation is still too high. A significant part of this uncertainty originates from the necessity to switch the KUP system frequently (every 12 min) for 6 min from ambient air to a working gas in order to correct short-term variations of the O2 measurement system. Allowing additional time for signal stabilization after switching the sample, an effective data coverage of only one-sixth for the KUP system is achieved while the Empa system has a nearly complete data coverage. Additionally, different internal volumes and flow rates may affect observed differences

Scattering matrices and expansion coefficients of Martian analogue palagonite particles

We present measurements of ratios of elements of the scattering matrix of Martian analogue palagonite particles for scattering angles ranging from 3 to 174 degrees and a wavelength of 632.8 nm. To facilitate the use of these measurements in radiative transfer calculations we have devised a method that enables us to obtain, from these measurements, a normalized synthetic scattering matrix covering the complete scattering angle range from 0 to 180 degrees. Our method is based on employing the coefficients of the expansions of scattering matrix elements into generalized spherical functions. The synthetic scattering matrix elements and/or the expansion coefficients obtained in this way, can be used to include multiple scattering by these irregularly shaped particles in (polarized) radiative transfer calculations, such as calculations of sunlight that is scattered in the dusty Martian atmosphere.Comment: 34 pages 7 figures 1 tabl

5d-5f Electric-multipole Transitions in Uranium Dioxide Probed by Non-resonant Inelastic X-ray Scattering

Non-resonant inelastic x ray scattering (NIXS) experiments have been performed to probe the 5d-5f electronic transitions at the uranium O(4,5) absorption edges in uranium dioxide. For small values of the scattering vector q, the spectra are dominated by dipole-allowed transitions encapsulated within the giant resonance, whereas for higher values of q the multipolar transitions of rank 3 and 5 give rise to strong and well-defined multiplet structure in the pre-edge region. The origin of the observed non-dipole multiplet structures is explained on the basis of many-electron atomic spectral calculations. The results obtained demonstrate the high potential of NIXS as a bulk-sensitive technique for the characterization of the electronic properties of actinide materials.Comment: Submitted to Physical Review Letters on 31 December 200

How does star formation proceed in the circumnuclear starburst ring of NGC 6951?

Gas inflowing along stellar bars is often stalled at the location of circumnuclear rings, that form an effective reservoir for massive star formation and thus shape the central regions of galaxies. However, how exactly star formation is proceeding within these circumnuclear starburst rings is subject of debate. Two main scenarios for this process have been put forward: In the first the onset of star formation is regulated by the total amount of gas present in the ring with star forming starting once a mass threshold has reached in a `random' position within the ring like `popcorn'. In the second star formation preferentially takes place near the locations where the gas enters the ring. This scenario has been dubbed `pearls-on-a-string'. Here we combine new optical IFU data covering the full stellar bar with existing multi-wavelength data to study in detail the 580 pc radius circumnuclear starburst ring in the nearby spiral galaxy NGC 6951. Using HST archival data together with Sauron and Oasis IFU data, we derive the ages and stellar masses of star clusters as well as the total stellar content of the central region. Adding information on the molecular gas distribution, stellar and gaseous dynamics and extinction, we find that the circumnuclear ring in NGC 6951 is ~1-1.5 Gyr old and has been forming stars for most of that time. We see evidence for preferred sites of star formation within the ring, consistent with the `pearls-on-a-string' scenario, when focusing on the youngest stellar populations. Due to the ring's longevity this signature is washed out when older stellar populations are included in the analysis.Comment: accepted for publication in A&A, 15 page

The Supernova Remnant CTB104A : Magnetic Field Structure and Interaction with the Environment

We present new, high resolution 1420 and 408 MHz continuum images and HI and 12CO (J=1-0) spectral line maps of the diffuse supernova remnant CTB104A (G93.7-0.3). Analysis of the complex continuum emission reveals no significant spectral index variations across the remnant. Three prominences around CTB104A are found to be related to the SNR, while one extension to the east is identified as an HII region associated with a background molecular shell. Small scale polarization and rotation measure (RM) structures are turbulent in nature, but we find a well-ordered RM gradient across the remnant, extending from southeast to northwest. This gradient does not agree with the direction of the global Galactic magnetic field, but does agree with a large-scale RM anomaly inferred from rotation measure data by Cleg et al. (1992). We show that the observed morphology of CTB104A is consistent with expansion in a uniform magnetic field, and this is supported by the observed RM distribution. By modeling the RM gradient with a simple compression model we have determined the magnetic field strength within the remnant as Bo ~ 2.3 micro G. We have identified signatures of the interaction of CTB104A with the surrounding neutral material, and determined its distance, from the kinematics of the HI structure encompassing the radio emission, as 1.5 kpc. We also observed clear breaks in the HI shell that correspond well to the positions of two of the prominences, indicating regions where hot gas is escaping from the interior of the SNR.Comment: 7 pages, Latex with aastex and emulateapj5, 12 figures, ApJ accepte

Comment on ``Spin Polarization and Magnetic Circular Dichroism in Photoemission from the 2p Core Level of Ferromagnetic Ni''

Although the Ni_4 cluster includes more information regarding the Ni band structure with respect to the Anderson impurity model, it also favors very peculiar ground states which are incompatible with a coherent picture of all dichroism experiments.Comment: 1 page, RevTeX, 1 epsf figur

Protection of stainless-steels against corrosion in sulphidizing environments by Ce oxide coatings: X-ray absorption and thermogravimetric studies

In this paper a study is reported concerning ceramic coatings containing cerium oxide, prepared by the sol-gel method, used to protect Incoloy 800H against sulphidation. When the coating is sintered in air at 850°C good protection is obtained. In an X-ray absorption spectroscopic study of the coatings it was observed that the best protective coating contains all cerium as CeIV after pretreatment. After sulphidizing cerium was reduced to CeIII. Possible mechanisms to explain the protective properties are discussed

Heating and cooling of the neutral ISM in the NGC4736 circumnuclear ring

The manner in which gas accretes and orbits within circumnuclear rings has direct implications for the star formation process. In particular, gas may be compressed and shocked at the inflow points, resulting in bursts of star formation at these locations. Afterwards the gas and young stars move together through the ring. In addition, star formation may occur throughout the ring, if and when the gas reaches sufficient density to collapse under gravity. These two scenarios for star formation in rings are often referred to as the `pearls on a string' and `popcorn' paradigms. In this paper, we use new Herschel PACS observations, obtained as part of the KINGFISH Open Time Key Program, along with archival Spitzer and ground-based observations from the SINGS Legacy project, to investigate the heating and cooling of the interstellar medium in the nearby star-forming ring galaxy, NGC4736. By comparing spatially resolved estimates of the stellar FUV flux available for heating, with the gas and dust cooling derived from the FIR continuum and line emission, we show that while star formation is indeed dominant at the inflow points in NGC 4736, additional star formation is needed to balance the gas heating and cooling throughout the ring. This additional component most likely arises from the general increase in gas density in the ring over its lifetime. Our data provide strong evidence, therefore, for a combination of the two paradigms for star formation in the ring in NGC4736.Comment: accepted for publication in A&

Social skills training for juvenile delinquents:Post-treatment changes

Objectives To examine the post-treatment effectiveness of an outpatient, individual social skills training for juvenile delinquents in the Netherlands and to conduct moderator tests for age, gender, ethnicity, and risk of reoffending. Methods The sample consisted of juveniles who received Tools4U, a social skills training with a parental component, as a penal sanction (N = 115). Propensity score matching was used to select a control group of juveniles receiving treatment as usual (TAU) of n = 108 juveniles (of a total of N = 354). Assessment of impulsivity, social perspective-taking, social problem-solving, critical reasoning, developmental task-related skills, and treatment integrity took place before and immediately after the treatment. Results Treatment integrity was found to be sufficient, so that treatment effects could be attributed to the Tools4U training. Tools4U was more effective than TAU in reducing impulsivity, cognitive distortions (self-centering and assuming the worst), and social perspective-taking deficits (hostile intent attribution). No treatment effects were found on adolescents’ social problem-solving skills, and only caretakers of girls showed improvement in parenting skills. Effects on developmental task-related skills were not in the expected direction: after Tools4U, juveniles reported significantly less social acceptance and self-worth than juveniles receiving TAU. Conclusions Tools4U showed generally small effects and no effects on protective factors, which might limit the long-term treatment effects on delinquency. Treatment effects may be improved by implementing additional techniques and improving the parental component for boys in particular