| 1. |
- Adler, SS, et al.
(författare)
-
Double helicity asymmetry in inclusive midrapidity pi(0) production for polarized p+p collisions at root s=200 GeV
- 2004
-
Ingår i: Physical Review Letters. - 1079-7114. ; 93:20: 202002
-
Tidskriftsartikel (refereegranskat)abstract
- We present a measurement of the double longitudinal spin asymmetry in inclusive pi(0) production in polarized proton-proton collisions at roots=200 GeV. The data were taken at the Relativistic Heavy Ion Collider with average beam polarizations of 0.27. The measurements are the first in a program to study the longitudinal spin structure of the proton, using strongly interacting probes, at collider energies. The asymmetry is presented for transverse momenta 1-5 GeV/c at midrapidity, where next-to-leading-order perturbative quantum chromodynamic (NLO pQCD) calculations well describe the unpolarized cross section. The observed asymmetry is small and is compared to a NLO pQCD calculation with a range of polarized gluon distributions.
|
|
| 2. |
- Rosser, Z H, et al.
(författare)
-
Y-chromosomal diversity in Europe is clinal and influenced primarily by geography, rather than by language.
- 2000
-
Ingår i: American Journal of Human Genetics. - : Elsevier BV. - 0002-9297 .- 1537-6605. ; 67:6, s. 1526-43
-
Tidskriftsartikel (refereegranskat)abstract
- Clinal patterns of autosomal genetic diversity within Europe have been interpreted in previous studies in terms of a Neolithic demic diffusion model for the spread of agriculture; in contrast, studies using mtDNA have traced many founding lineages to the Paleolithic and have not shown strongly clinal variation. We have used 11 human Y-chromosomal biallelic polymorphisms, defining 10 haplogroups, to analyze a sample of 3,616 Y chromosomes belonging to 47 European and circum-European populations. Patterns of geographic differentiation are highly nonrandom, and, when they are assessed using spatial autocorrelation analysis, they show significant clines for five of six haplogroups analyzed. Clines for two haplogroups, representing 45% of the chromosomes, are continentwide and consistent with the demic diffusion hypothesis. Clines for three other haplogroups each have different foci and are more regionally restricted and are likely to reflect distinct population movements, including one from north of the Black Sea. Principal-components analysis suggests that populations are related primarily on the basis of geography, rather than on the basis of linguistic affinity. This is confirmed in Mantel tests, which show a strong and highly significant partial correlation between genetics and geography but a low, nonsignificant partial correlation between genetics and language. Genetic-barrier analysis also indicates the primacy of geography in the shaping of patterns of variation. These patterns retain a strong signal of expansion from the Near East but also suggest that the demographic history of Europe has been complex and influenced by other major population movements, as well as by linguistic and geographic heterogeneities and the effects of drift.
|
|
| 3. |
- Kasic, A., et al.
(författare)
-
Phonons and free-carrier properties of binary, ternary, and quaternary group-III nitride layers measured by infrared Spectroscopic Ellipsometry
- 2003
-
Ingår i: Physica Status Solidi. C, Current topics in solid state physics. - : Wiley. - 1610-1634 .- 1610-1642. ; 0:6 SPEC. ISS., s. 1750-1769
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This work reviews recent ellipsometric investigations of the infrared dielectric functions of binary, ternary, and quaternary group-III nitride films. Spectroscopic Ellipsometry in the mid-infrared range is employed for the first time to determine phonon and free-carrier properties of individual group-III nitride heterostructure components, including layers of some ten nanometer thickness. Assuming the effective carrier mass, the free-carrier concentration and mobility parameters can be quantified upon model analysis of the infrared dielectric function. In combination with Hall-effect measurements, the effective carrier masses for wurtzite n- and p-type GaN and n-type InN are obtained. The mode behavior of both the E1(TO) and A1(LO) phonons are determined for ternary compounds. For strain-sensitive phonon modes, the composition and strain dependences of the phonon frequencies are differentiated and quantified. Information on the crystal quality and compositional homogeneity of the films can be extracted from the phonon mode broadening parameters. A comprehensive IR dielectric function database of group-III nitride materials has been established and can be used for the analysis of complex thin-film heterostructures designed for optoelectronic device applications. Information on concentration and mobility of free carriers, thickness, alloy composition, average strain state, and crystal quality of individual sample constituents can be derived. © 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
|
|
| 4. |
|
|
| 5. |
|
|
| 6. |
- Johansson, Erik, et al.
(författare)
-
Street canyon microclimate in traditional and modern neighbourhoods in a hot dry climate - a case study in Fez, Morocco
- 2001
-
Ingår i: [Host publication title missing]. ; 2, s. 661-665
-
Konferensbidrag (refereegranskat)abstract
- The urban climate can vary considerably within cities. In a hot and dry climate, the micro¬climate at street level depends to a large extent on the urban geometry and building density. To be able to plan and design comfortable urban areas in the future, it is important to understand how different urban textures influence the climate. This paper deals with a case study in Fez, Morocco, where climate measurements took place in two entirely different types of neighbourhoods: a modern, suburban area with wide streets and many open spaces and a traditional, dense neighbourhood in the old city. The results show significant differences between the two neighbourhoods. In both summer and winter the minimum temperature was 2–4°C lower in the modern area, and the maximum temperature was about 10°C higher. In summer the modern area was extremely uncomfortable whereas the traditional was within the comfort zone. In winter neither area achieved comfort, but the modern was better.
|
|
| 7. |
- Pereira, Mauro F, et al.
(författare)
-
Controlling many-body effects in the midinfrared gain and terahertz absorption of quantum cascade laser structures
- 2004
-
Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 69
-
Tidskriftsartikel (refereegranskat)abstract
- A many-body theory based on nonequilibrium Green functions, in which transport and optics are treated on a microscopic quantum-mechanical basis, is used to compute gain and absorption in the optical and terahertz regimes in quantum cascade laser structures. The relative importance of Coulomb interactions for different intersubband transitions depends strongly on the spatial overlap of the wave functions and the specific nonequilibrium populations within the subbands. The magnitude of the Coulomb effects can be controlled by changing the operation bias.
|
|
| 8. |
- Pereira, M.F., et al.
(författare)
-
Nonequilibrium and many body effects in the realistic simulation of intersubband emitters
- 2004
-
Ingår i: Proceedings of the 4th International Conference on Numerical Simulation of Optoelectronic Devices, 2004. NUSOD '04.. - 0780385306 ; , s. 94-96
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This study gives a short description of nonequilibrium and many body effects in realistic simulation of intersubband emitters. Calculations are based on the self-consistent solution of the quantum kinetic equations under operating steady-state conditions. Scattering with phonons is included by means of a self-energy in the Dyson equation, and electron-electron interaction is treated in mean field approximation.
|
|
| 9. |
|
|
