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| 2. |
- Bruzzi, M, et al.
(författare)
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Radiation-hard semiconductor detectors for SuperLHC
- 2005
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Ingår i: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - : Elsevier BV. - 0167-5087 .- 0168-9002. ; 541:1-2, s. 189-201
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Tidskriftsartikel (refereegranskat)abstract
- An option of increasing the luminosity of the Large Hadron Collider (LHC) at CERN to 1035 cm-2 s-1 has been envisaged to extend the physics reach of the machine. An efficient tracking down to a few centimetres from the interaction point will be required to exploit the physics potential of the upgraded LHC. As a consequence, the semiconductor detectors close to the interaction region will receive severe doses of fast hadron irradiation and the inner tracker detectors will need to survive fast hadron fluences of up to above 1016cm-2. The CERN-RD50 project "Development of Radiation Hard Semiconductor Devices for Very High Luminosity Colliders" has been established in 2002 to explore detector materials and technologies that will allow to operate devices up to, or beyond, this limit. The strategies followed by RD50 to enhance the radiation tolerance include the development of new or defect engineered detector materials (SiC, GaN, Czochralski and epitaxial silicon, oxygen enriched Float Zone silicon), the improvement of present detector designs and the understanding of the microscopic defects causing the degradation of the irradiated detectors. The latest advancements within the RD50 collaboration on radiation hard semiconductor detectors will be reviewed and discussed in this work.
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| 3. |
- Tabassum, R, et al.
(författare)
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Genetic architecture of human plasma lipidome and its link to cardiovascular disease
- 2019
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Ingår i: Nature communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 10:1, s. 4329-
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Tidskriftsartikel (refereegranskat)abstract
- Understanding genetic architecture of plasma lipidome could provide better insights into lipid metabolism and its link to cardiovascular diseases (CVDs). Here, we perform genome-wide association analyses of 141 lipid species (n = 2,181 individuals), followed by phenome-wide scans with 25 CVD related phenotypes (n = 511,700 individuals). We identify 35 lipid-species-associated loci (P <5 ×10−8), 10 of which associate with CVD risk including five new loci-COL5A1, GLTPD2, SPTLC3, MBOAT7 and GALNT16 (false discovery rate<0.05). We identify loci for lipid species that are shown to predict CVD e.g., SPTLC3 for CER(d18:1/24:1). We show that lipoprotein lipase (LPL) may more efficiently hydrolyze medium length triacylglycerides (TAGs) than others. Polyunsaturated lipids have highest heritability and genetic correlations, suggesting considerable genetic regulation at fatty acids levels. We find low genetic correlations between traditional lipids and lipid species. Our results show that lipidomic profiles capture information beyond traditional lipids and identify genetic variants modifying lipid levels and risk of CVD.
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| 4. |
- Chyz̊y, K.T., et al.
(författare)
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LOFAR MSSS: Flattening low-frequency radio continuum spectra of nearby galaxies
- 2018
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 619
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Tidskriftsartikel (refereegranskat)abstract
- Aims. The shape of low-frequency radio continuum spectra of normal galaxies is not well understood, the key question being the role of physical processes such as thermal absorption in shaping them. In this work we take advantage of the LOFAR Multifrequency Snapshot Sky Survey (MSSS) to investigate such spectra for a large sample of nearby star-forming galaxies. Methods. Using the measured 150 MHz flux densities from the LOFAR MSSS survey and literature flux densities at various frequencies we have obtained integrated radio spectra for 106 galaxies characterised by different morphology and star formation rate. The spectra are explained through the use of a three-dimensional model of galaxy radio emission, and radiation transfer dependent on the galaxy viewing angle and absorption processes. Results. Our galaxies' spectra are generally flatter at lower compared to higher frequencies: the median spectral index αlow measured between ≈ 50 MHz and 1.5 GHz is -0.57 ± 0.01 while the high-frequency one αhigh, calculated between 1.3 GHz and 5 GHz, is -0.77 ± 0.03. As there is no tendency for the highly inclined galaxies to have more flattened low-frequency spectra, we argue that the observed flattening is not due to thermal absorption, contradicting the suggestion of Israel & Mahoney (1990, ApJ, 352, 30). According to our modelled radio maps for M 51-like galaxies, the free-free absorption effects can be seen only below 30 MHz and in the global spectra just below 20 MHz, while in the spectra of starburst galaxies, like M 82, the flattening due to absorption is instead visible up to higher frequencies of about 150 MHz. Starbursts are however scarce in the local Universe, in accordance with the weak spectral curvature seen in the galaxies of our sample. Locally, within galactic disks, the absorption effects are distinctly visible in M 51-like galaxies as spectral flattening around 100-200 MHz in the face-on objects, and as turnovers in the edge-on ones, while in M 82-like galaxies there are strong turnovers at frequencies above 700 MHz, regardless of viewing angle. Conclusions. Our modelling of galaxy spectra suggests that the weak spectral flattening observed in the nearby galaxies studied here results principally from synchrotron spectral curvature due to cosmic ray energy losses and propagation effects. We predict much stronger effects of thermal absorption in more distant galaxies with high star formation rates. Some influence exerted by the Milky Way's foreground on the spectra of all external galaxies is also expected at very low frequencies.
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| 5. |
- Bowden, John A., et al.
(författare)
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Harmonizing lipidomics : NIST interlaboratory comparison exercise for lipidomics using SRM 1950-Metabolites in Frozen Human Plasma
- 2017
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Ingår i: Journal of Lipid Research. - 0022-2275 .- 1539-7262. ; 58:12, s. 2275-2288
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Tidskriftsartikel (refereegranskat)abstract
- As the lipidomics field continues to advance, self-evaluation within the community is critical. Here, we performed an interlaboratory comparison exercise for lipidomics using Standard Reference Material (SRM) 1950-Metabolites in Frozen Human Plasma, a commercially available reference material. The interlaboratory study comprised 31 diverse laboratories, with each laboratory using a different lipidomics workflow. A total of 1,527 unique lipids were measured across all laboratories and consensus location estimates and associated uncertainties were determined for 339 of these lipids measured at the sum composition level by five or more participating laboratories. These evaluated lipids detected in SRM 1950 serve as community-wide benchmarks for intra-and interlaboratory quality control and method validation. These analyses were performed using nonstandardized laboratory-independent workflows. The consensus locations were also compared with a previous examination of SRM 1950 by the LIPID MAPS consortium.jlr While the central theme of the interlaboratory study was to provide values to help harmonize lipids, lipid mediators, and precursor measurements across the community, it was also initiated to stimulate a discussion regarding areas in need of improvement.
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| 6. |
- Kaczmarczyk, M, et al.
(författare)
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Comprehensive study of InAs/GaAs quantum dots by means of complementary methods
- 2009
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Ingår i: Materials Science & Engineering B: Solid-State Materials for Advanced Technology. - : Elsevier BV. - 0921-5107. ; 165:1-2, s. 98-102
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Konferensbidrag (refereegranskat)abstract
- Structural, optical, and electronic properties of self-organized InAs/GaAs quantum dots (QDs) were studied by means of atomic force microscopy (AFM), photoluminescence measurements (PL), and deep level transient spectroscopy (DLTS). We found that a well defined group of QDs with low size dispersion as revealed by AFM maintains its properties in PL spectra even if the QDs are covered by GaAs. Two well separated emission lines attributed to the QD-related ground- and excited-state transitions. respectively are found in the PL spectra. Contrary to the optical picture of a characteristic simplicity, DLTS spectra are found with higher complexity. This is due to combined thermal/tunneling processes and multi-particle emission. Despite the relatively good understanding of optical and electrical properties of QDs in PL and DLTS, respectively, there are still discrepancies between electrical and optical data for the energy of the QD ground states, which need more investigations to be explained.
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| 8. |
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| 9. |
- Kaniewska, M., et al.
(författare)
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Hole emission mechanism in Ge/Si quantum dots
- 2011
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Ingår i: Physica Status Solidi (C) Current Topics in Solid State Physics. - : Wiley. - 1610-1642 .- 1862-6351. ; 8:2, s. 411 -413
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Tidskriftsartikel (refereegranskat)abstract
- The mechanisms determining emission of holes in self-assembled Ge quantum dots (QDs) embedded in the p-type Si matrix have been investigated. Specimens were prepared by molecular beam epitaxy (MBE). Electrical methods such as deep level transient spectroscopy (DLTS) and capacitance versus voltage (C-V) measurements were used for the study. The emission mechanisms were identified by measuring a QD-related signal as a function of the repetition frequency of the filling pulses with the reverse voltage and the pulse voltage as a parameter. An observed shift of the signal position or its absence versus the voltage parameters was interpreted in terms of thermal, tunnelling and mixed processes and attributed to the presence of a Coulomb barrier formed as a result of the charging effect. Thermal emission properties of the QDs were characterized under such measurement conditions that tunnelling contributions to the DLTS spectra could be neglected.
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| 10. |
- Kaniewska, M., et al.
(författare)
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Spatial variarion of hole eigen energies in Ge/Si quantum wells
- 2011
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Ingår i: AIP Conference Proceedings. - : AIP. - 1551-7616 .- 0094-243X. - 9780735410022 ; 1399, s. 293-294
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Konferensbidrag (refereegranskat)abstract
- Ge quantum well (QW) structures were prepared through Si-capping of 3.3 ML of Ge by MBE on p +-(001) Si substrates at a growth temperature of 550°C. The spatial variation of hole eigen energies in the QW were revealed by DLTS. Depending on the position on the wafer surface, the hole emission may be imposed by a lateral quantum confinement effect. Results of a study by HRTEM methods demonstrate pronounced fluctuations of the QW thickness and variations of the strain field in the QW.
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