22,652 research outputs found
Recommended from our members
Changing the way we learn: towards agile learning and co-operation
This paper addresses the need for learning and competence development in industrial organizations. The people that enter professional organizations today are part of a gamer generation that have some or much experience with on-line games. Therefore they are more open to e-learning and in general more open to access anything on-line. At the same time industrial organizations experience a pressure on their ability to train employees faster due to the increase in complexity. We argue that games are not yet mature enough to support this training challenge as stand alone efforts. But games can support the training and competence development in a synchronized setup with other means
Estimation in a growth study with irregular measurement times
Between 1982 and 1988 a growth study was carried out at the Division of Pediatric Oncology of the University Hospital of Groningen. A special feature of the project was that sample sizes are small and that ages at entry may be very different. In addition the intended design was not fully complied with. This paper highlights some aspects of the statistical analysis which is based on (1) reference scores, (2) statistical procedures allowing for an irregular pattern of measurement times caused by missing data and shifted measurement times
A Face-On Tully-Fisher Relation
We construct the first "face-on" Tully-Fisher (TF) relation for 24 galaxies
with inclinations between 16 degrees and 41 degrees. The enabling measurements
are integral-field, echelle spectroscopy from the WIYN 3.5m telescope, which
yield accurate kinematic estimates of disk inclination to 15 degrees. Kinematic
inclinations are of sufficient accuracy that our measured TF scatter of 0.42
mag is comparable to other surveys even without internal-absorption
corrections. Three of four galaxies with significant kinematic and photometric
asymmetries also have the largest deviations from our TF relation, suggesting
that asymmetries make an important contribution to TF scatter. By measuring
inclinations below 40 degrees, we establish a direct path to linking this
scatter to the unprojected structure of disks and making non-degenerate
dynamical mass-decompositions of spiral galaxies.Comment: 13 pages, 3 figures (2 color). Accepted for publication in ApJ
Letter
Electronic structure and magnetism in doped semiconducting half-Heusler compounds
We have studied in details the electronic structure and magnetism in M (Mn
and Cr) doped semiconducting half-Heusler compounds FeVSb, CoTiSb and NiTiSn
(XMYZ) in a wide concentration range using local-spin density
functional method in the framework of tight-binding linearized muffin tin
orbital method(TB-LMTO) and supercell approach. Our calculations indicate that
some of these compounds are not only ferromagnetic but also half-metallic and
may be useful for spintronics applications. The electronic structure of the
doped systems is analyzed with the aid of a simple model where we have
considered the interaction between the dopant transition metal (M) and the
valence band X-Z hybrid. We have shown that the strong X-d - M-d interaction
places the M-d states close to the Fermi level with the M-t states lying
higher in energy in comparison to the M-e states. Depending on the number
of available d-electrons, ferromagnetism is realized provided the d-manifold is
partially occupied. The tendencies toward ferromagnetic(FM) or
antiferromagnetic(AFM) behavior are discussed within Anderson-Hasegawa models
of super-exchange and double-exchange. In our calculations for Mn doped NiTiSn,
the strong preference for FM over AFM ordering suggests a possible high Curie
temperature for these systems.Comment: 14 pages, 6 figure
Electron-phonon interaction in Graphite Intercalation Compounds
Motivated by the recent discovery of superconductivity in Ca- and
Yb-intercalated graphite (CaC and YbC) and from the ongoing debate
on the nature and role of the interlayer state in this class of compounds, in
this work we critically study the electron-phonon properties of a simple model
based on primitive graphite. We show that this model captures an essential
feature of the electron-phonon properties of the Graphite Intercalation
Compounds (GICs), namely, the existence of a strong dormant electron-phonon
interaction between interlayer and electrons, for which we
provide a simple geometrical explanation in terms of NMTO Wannier-like
functions. Our findings correct the oversimplified view that
nearly-free-electron states cannot interact with the surrounding lattice, and
explain the empirical correlation between the filling of the interlayer band
and the occurrence of superconductivity in Graphite-Intercalation Compounds.Comment: 13 pages, 12 figures, submitted to Phys. Rev.
Variational study of the antiferromagnetic insulating phase of V2O3 based on Nth order Muffin-Tin-Orbitals
Motivated by recent results of th order muffin-tin orbital (NMTO)
implementation of the density functional theory (DFT), we re-examine
low-temperature ground-state properties of the anti-ferromagnetic insulating
phase of vanadium sesquioxide VO. The hopping matrix elements obtained
by the NMTO-downfolding procedure differ significantly from those previously
obtained in electronic structure calculations and imply that the in-plane
hopping integrals are as important as the out-of-plane ones. We use the NMTO
hopping matrix elements as input and perform a variational study of the ground
state. We show that the formation of stable molecules throughout the crystal is
not favorable in this case and that the experimentally observed magnetic
structure can still be obtained in the atomic variational regime. However the
resulting ground state (two electrons occupying the degenerate
doublet) is in contrast with many well established experimental observations.
We discuss the implications of this finding in the light of the non-local
electronic correlations certainly present in this compound.Comment: 7 pages, 2 figure
Magnetic properties of PdAs2O6: a dilute spin system with an unusually high N\'eel temperature
The crystal structure and magnetic ordering pattern of PdAs2O6 were
investigated by neutron powder diffraction. While the magnetic structure of
PdAs2O6 is identical to the one of its isostructural 3d-homologue NiAs2O6, its
N\'{e}el temperature (140 K) is much higher than the one of NiAs2O6 (30 K).
This is surprising in view of the long distance and indirect exchange path
between the magnetic Pd ions. Density functional calculations yield
insight into the electronic structure and the geometry of the exchange-bond
network of both PdAs2O6 and NiAs2O6, and provide a semi-quantitative
explanation of the large amplitude difference between their primary exchange
interaction parameters
Pea-barley intercrop N dynamics in farmers fields
Knowledge about crop performances in farmers’ fields provides a link between on-farm practice and re-search. Thereby scientists may improve their ability to understand and suggest solutions for the problems facing those who have the responsibility of making sound agricultural decisions.
Nitrogen (N) availability is known to be highly heterogeneous in terrestrial plant communities (Stevenson and van Kessel, 1997), a heterogeneity that in natural systems is often associated with variation in the distri-bution of plant species. In intercropping systems the relative proportion of component crops is influenced by the distribution of growth factors such as N in both time and space (Jensen, 1996). In pea-barley intercrops, an increase in the N supply promotes the growth of barley thereby decreasing the N accumulation of pea and giving rise to changes in the relative proportions of the intercropped components (Jensen, 1996). The pres-sure of weeds may, however, significantly change the dynamics in intercrops (Hauggaard-Nielsen et al., 2001). Data from farmers’ fields may provide direct, spatially explicit information for evaluating the poten-tials of improving the utilisation of field variability by intercrops
- …