Cluster analysis of the impact of air back-trajectories on aerosol optical properties at Hornsund, Spitsbergen

In this paper, spectra of aerosol optical thickness from the AERONET (AErosol RObotic NETwork) station at Hornsund in the southern part of Spitsbergen were employed to study the impact of air mass history on aerosol optical thickness for wavelength λ=500 nm – AOT(500) – and the Ångström exponent. Backward trajectories computed, using the NOAA HYSPLIT model, were used to trace air history. It was found that in spring, the changes in AOT values over the Hornsund station were strongly influenced by air mass trajectories 8 days or longer in duration, arriving both in the free troposphere and at an altitude of 1 km above sea level. Nevertheless, free tropospheric advection was dominant. AOT variability in summer was best explained by the local direction and speed of advection (1-day trajectories) and was dominated by the effectiveness of cleansing processes. During the ASTAR 2007 campaign, the aerosols near Hornsund displayed low AOT values ranging from 0.06 to 0.09, which is lower than the mean AOT(500) for spring seasons from 2005 to 2007 (0.110±0.007; mean ± standard deviation of mean). 9 April 2007 with AOT(500)=0.147 was exceptional. The back-trajectories belonged to clusters with low and average cluster mean AOT. Apart from the maximum AOT of 9 April 2007, the observed AOT values were close to or lower than the means for the clusters to which they belonged

On piecewise trivial Hopf—Galois extensions

We discuss a noncommutative generalization of compact principal bundles that can be trivialized relative to the finite covering by closed sets. In this setting we present bundle reconstruction and reduction

Photo-induced relaxation of magnetization in molecular magnet

The experimental study of photo-induced magnetization of hybrid molecular magnet containing cobalt(II) and tungsten(V) magnetic centers bridged by 4,40 -bpy and CN− is presented. The observed increase in magnetization rate is attributed to the defects due to inter-valence transfer between CoIIWV *) CoIIIWIV. The time evolution of magnetization is parameterized by the power law rather than exponential function

System Response Kernel Calculation for List-mode Reconstruction in Strip PET Detector

Reconstruction of the image in Positron Emission Tomographs (PET) requires the knowledge of the system response kernel which describes the contribution of each pixel (voxel) to each tube of response (TOR). This is especially important in list-mode reconstruction systems, where an efficient analytical approximation of such function is required. In this contribution, we present a derivation of the system response kernel for a novel 2D strip PET.Comment: 10 pages, 2 figures; Presented at Symposium on applied nuclear physics and innovative technologies, Cracow, 03-06 June 201

Beam profile investigation of the new collimator system for the J-PET detector

Jagiellonian Positron Emission Tomograph (J-PET) is a multi-purpose detector which will be used for search for discrete symmetries violations in the decays of positronium atoms and for investigations with positronium atoms in life-sciences and medical diagnostics. In this article we present three methods for determination of the beam profile of collimated annihilation gamma quanta. Precise monitoring of this profile is essential for time and energy calibration of the J-PET detector and for the determination of the library of model signals used in the hit-time and hit-position reconstruction. We have we have shown that usage of two lead bricks with dimensions of 5x10x20 cm^3 enables to form a beam of annihilation quanta with Gaussian profile characterized by 1 mm FWHM. Determination of this characteristic is essential for designing and construction the collimator system for the 24-module J-PET prototype. Simulations of the beam profile for different collimator dimensions were performed. This allowed us to choose optimal collimation system in terms of the beam profile parameters, dimensions and weight of the collimator taking into account the design of the 24 module J-PET detector.Comment: 14 pages, 9 figure

Measurement of the invariant mass distributions for the pp -> ppeta' reaction at excess energy of Q = 16.4 MeV

The proton-proton and proton-eta' invariant mass distributions have been determined for the pp -> ppeta' reaction at an excess energy of Q = 16.4 MeV. The measurement was carried out using the COSY-11 detector setup and the proton beam of the cooler synchrotron COSY. The shapes of the determined invariant mass distributions are similar to those of the pp -> ppeta reaction and reveal an enhancement for large relative proton-proton momenta. This result, together with the fact that the proton-eta interaction is much stronger that the proton-eta' interaction, excludes the hypothesis that the observed enhancement is caused by the interaction between the proton and the meson