228 research outputs found
First performance evaluation of a Multi-layer Thick Gaseous Electron Multiplier with in-built electrode meshes - MM-THGEM
We describe a new micro-pattern gas detector structure comprising a
multi-layer hole-type multiplier (M-THGEM) combined with two in-built electrode
meshes: the Multi-Mesh THGEM-type multiplier (MM-THGEM). Suitable potential
differences applied between the various electrodes provide an efficient
collection of ionization electrons within the MM-THGEM holes and a large charge
avalanche multiplication between the meshes. Different from conventional
hole-type multipliers (e.g. Gas Electron Multipliers - GEMs, Thick Gas Electron
Multipliers - THGEMs, etc.), which are characterized by a variable
(dipole-like) field strength inside the avalanche gap, electrons in MM-THGEMs
are largely multiplied by a strong uniform field established between the two
meshes, like in the parallel-plate avalanche geometry. The presence of the two
meshes within the holes allows for the trapping of a large fraction of the
positive ions that stream back to the drift region. A gas gain above 10^5 has
been achieved for single photo-electron detection with a single MM-THGEM in
Ar/(10%)CH4 and He/(10%)CO2, at standard conditions for temperature and
pressure. When the MM-THGEM is coupled to a conventional THGEM and used as
first cascade element, the maximum achievable gains reach values above 10^6 in
He/(10%)CO2, while the IBF approaches of 1.5% in the case of optimum
detector-bias configuration. This IBF value is several times lower compared to
the one obtained by a double GEM/THGEM detector (5-10%), and equivalent to the
performance attained by a Micromegas detector.Comment: 11 pages, 8 figures. Submitted to JINS
The revised Brussels-Locarno Sunspot Number (1981-2015)
In 1981, the production of the international Sunspot Number moved from the
Z\"{u}rich Observatory to the Royal Observatory of Belgium, marking a very
important transition in the history of the Sunspot Number. Those recent decades
are particularly important for linking recent modern solar indices and fluxes
and the past Sunspot Number series. However, large variations have been
recently identified in the scale of the Sunspot Number between 1981 and the
present.
Here, we reconstruct a new average Sunspot Number series using
long-duration stations between 1981 and 2015. We also extend this
reconstruction using long-time series from 35 stations over 1945-2015, which
includes the 1981 transition. In both reconstructions, we also derive a
parallel Group Number series . Our results confirm the variable trends of
the Locarno pilot station. We also verify the scale of the resulting 1981-2015
correction factor relative to the preceding period 1945--1980. By comparing the
new and series, we find that a constant quadratic relation exists
between those two indices. This proxy relation leads to a fully constant and
cycle-independent ratio over cycles 19 to 23, with the exception of
cycle 24. We find a very good agreement between our reconstructed and the
new "backbone" Group Number but inhomogeneities in the original Group Number as
well as the radio flux and the American sunspot number .
This analysis opens the way to the implementation of a more advanced method
for producing the Sunspot Number in the future. In particular, we identify the
existence of distinct subsets of observing stations sharing very similar
personal k factors, which may be a key element for building a future
multi-station reference in place of the past single pilot station.Comment: 33 pages, 23 figures, 2 table
Fiber Thickness and Porosity Control in a Biopolymer Scaffold 3D Printed through a Converted Commercial FDM Device
3D printing has opened exciting new opportunities for the in vitro fabrication of biocompatible hybrid pseudo-tissues. Technologies based on additive manufacturing herald a near future when patients will receive therapies delivering functional tissue substitutes for the repair of their musculoskeletal tissue defects. In particular, bone tissue engineering (BTE) might extensively benefit from such an approach. However, designing an optimal 3D scaffold with adequate stiffness and biodegradability properties also guaranteeing the correct cell adhesion, proliferation, and differentiation, is still a challenge. The aim of this work was the rewiring of a commercial fuse deposition modeling (FDM) 3D printer into a 3D bioplotter, aiming at obtaining scaffold fiber thickness and porosity control during its manufacturing. Although it is well-established that FDM is a fast and low-price technology, the high temperatures required for printing lead to limitations in the biomaterials that can be used. In our hands, modifying the printing head of the FDM device with a custom-made holder has allowed to print hydrogels commonly used for embedding living cells. The results highlight a good resolution, reproducibility and repeatability of alginate/gelatin scaffolds obtained via our custom 3D bioplotter prototype, showing a viable strategy to equip a small-medium laboratory with an instrument for manufacturing good-quality 3D scaffolds for cell culture and tissue engineering applications
Mitochondrial cytochrome b DNA sequence variations: an approach to fish species identification in processed fish products.
The identification of fish species in food products is problematic because morphological features of the fish are partially or completely lost during processing. It is important to determine fish origin because of the increasing international seafood trade and because European Community Regulation 104/2000 requires that the products be labeled correctly. Sequence analysis of PCR products from a conserved region of the cytochrome b gene was used to identity fish species belonging to the families Gadidae and Merluccidae in 18 different processed fish products. This method allowed the identification of fish species in all samples. Fish in all of the examined products belonged to these two families, with the exception of one sample of smoked baccalà (salt cod), which was not included in the Gadidae cluster
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