624 research outputs found
Development of Urban Electric Bus Drivetrain
The development of the drivetrain for a new series of urban electric buses is presented in the paper. The traction and design properties of several drive variants are compared. The efficiency of the drive was tested using simulation calculations of the vehicle rides based on data from real bus lines in Prague. The results of the design work and simulation calculations are presented in the paper
Changes in soil properties and possibilities of reducing environmental risks due to the application of biological activators in conditions of very heavy soils
This study aims at verifying the effect of farmyard manure (FYM) and of selected
activators (Z'fix and NeoSol) on changes of soil properties. Their application should lead to
improvement of soil physical properties and of organic matter fixation, to reduction of
environmental risks, e.g. of tillage energy requirements. Experimental variants (0.7 ha each) were
as follows: I (FYM with Z'fix); II (FYM with Z'fix + NeoSol); III (FYM); IV (Control NPK only).
FYM was applied at rates: 50 t ha-1
(2014); 30 t ha-1
(2016). Additional NPK fertilizer (I–IV) was
applied according to annual crop nutrient normative. The agent Z'fix was used as an activator of
FYM biological transformation (5.5 kg t
-1
). The agent NeoSol was used as soil activator
(200 kg ha-1
; annually). In order to verify the effect, cone index, bulk density, tillage implement
draft and chemical soil components (Humus, C/N ration and Ntot) were measured annually.
Compared to the control, the application of FYM combined with the mentioned agents (I–III)
increased Ntot more than two times. Moreover, it decreased (I–III) bulk density by 8.7%. Tillage
implement draft decreased by 3% after the application of FYM with Z’fix (I, II). The study
confirmed that FYM application combined with utilization of activators positively influenced soil
fertility and helped to reduce environmental risks
The role of cytokinins in clubroot disease
Clubroot (Plasmodiophora brassicae) is a pathogen of Brassicaceae that causes significant reductions in yield as a consequence of gall formation in the root and hypocotyl of infected plants. The pathogen hijacks host vascular cambium development, and cytokinins are implicated in this process. This paper uses transcriptomics and metabolomics to investigate changes in cytokinin metabolism during gall formation of clubroot-infected Arabidopsis thaliana. RNASeq analysis of infected tissue showed that host cytokinin metabolism was strongly down-regulated both at the onset and late stages of gall formation. Expression of host genes associated with cytokinin biosynthesis, signalling, degradation and conjugation was strongly repressed. Analysis of cytokinin precursors, active components and conjugates by microanalytical techniques was consistent with these transcriptional responses. Two isopentenyltransferase genes associated with cytokinin biosynthesis are present in the P. brassicae genome and are expressed throughout gall formation. The impact of pathogen-derived cytokinins on the total cytokinin content of infected tissue and host gene expression was minimal in wild type plants. However, infection of ipt1;3;5;7 mutants that are severely restricted in their ability to synthesise active cytokinins led to an increase in expression of host cytokinin-responsive genes. We interpret these results as indicating that P. brassicae can synthesise small amounts of cytokinin, but this has little impact on the host plant as the ipt1;3;5;7 phenotype is not rescued. Intriguingly, plasmodial development was slowed and spore viability reduced in these mutants indicating a potential role for cytokinins in plasmodial development
Electronic structure of ferromagnetic semiconductor Ga1-xMnxAs probed by sub-gap magneto-optical spectroscopy
We employ Faraday and Kerr effect spectroscopy in the infrared range to
investigate the electronic structure of Ga1-xMnxAs near the Fermi energy. The
band structure of this archetypical dilute-moment ferromagnetic semiconductor
has been a matter of controversy, fueled partly by previous measurements of the
unpolarized infrared absorption and their phenomenological impurity-band
interpretation. The infrared magneto-optical effects we study arise directly
from the spin-splitting of the carrier bands and their chiral asymmetry due to
spin-orbit coupling. Unlike the unpolarized absorption, they are intimately
related to ferromagnetism and their interpretation is much more microscopically
constrained in terms of the orbital character of the relevant band states. We
show that the conventional theory of the disordered valence band with dominant
As p-orbital character and coupled by kinetic-exchange to Mn local moments
accounts semi-quantitatively for the overall characteristics of the measured
infrared magneto-optical spectra.Comment: 4 pages 3 figure
Mn incorporation in as-grown and annealed (Ga,Mn)As layers studied by x-ray diffraction and standing-wave uorescence
A combination of high-resolution x-ray diffraction and a new technique of
x-ray standing wave uorescence at grazing incidence is employed to study the
structure of (Ga,Mn)As diluted magnetic semiconductor and its changes during
post-growth annealing steps. We find that the film is formed by a uniform,
single crystallographic phase epilayer covered by a thin surface layer with
enhanced Mn concentration due to Mn atoms at random non-crystallographic
positions. In the epilayer, Mn incorporated at interstitial position has a
dominant effect on lattice expansion as compared to substitutional Mn. The
expansion coeffcient of interstitial Mn estimated from our data is consistent
with theory predictions. The concentration of interstitial Mn and the
corresponding lattice expansion of the epilayer are reduced by annealing,
accompanied by an increase of the density of randomly distributed Mn atoms in
the disordered surface layer. Substitutional Mn atoms remain stable during the
low-temperature annealing.Comment: 9 pages, 9 figure
Microscopic analysis of the valence band and impurity band theories of (Ga,Mn)As
We analyze microscopically the valence and impurity band models of
ferromagnetic (Ga,Mn)As. We find that the tight-binding Anderson approach with
conventional parameterization and the full potential LDA+U calculations give a
very similar picture of states near the Fermi energy which reside in an
exchange-split sp-d hybridized valence band with dominant orbital character of
the host semiconductor; this microscopic spectral character is consistent with
the physical premise of the k.p kinetic-exchange model. On the other hand, the
various models with a band structure comprising an impurity band detached from
the valence band assume mutually incompatible microscopic spectral character.
By adapting the tight-binding Anderson calculations individually to each of the
impurity band pictures in the single Mn impurity limit and then by exploring
the entire doping range we find that a detached impurity band does not persist
in any of these models in ferromagnetic (Ga,Mn)As.Comment: 29 pages, 25 figure
Disorder induced critical phenomena in magnetically glassy Cu-Al-Mn alloys
Measurements of magnetic hysteresis loops in Cu-Al-Mn alloys of different Mn
content at low temperatures are presented. The loops are smooth and continuous
above a certain temperature, but exhibit a magnetization discontinuity below
that temperature. Scaling analysis suggest that this system displays a disorder
induced phase transition line. Measurements allow to determine the critical
exponents and in agreement
with those reported recently [Berger et al., Phys. Rev. Lett. {\bf 85}, 4176
(2000)]Comment: 4 pages, 5 figure
Parental heights and maternal education as predictors of length/height of children at birth, age 3 and 19 years, independently on diet: the ELSPAC study
BACKGROUND/OBJECTIVES: Little is currently known about the relationship between the parental diet during pregnancy and the growth of the child from early childhood until early adulthood. This study was designed to examine whether the dietary patterns of the parents during a pregnancy and of the respective child at 3 years are associated with the length/height-for-age z-score of child at birth, 3 years of age and at 19 years of age. SUBJECTS/METHODS: Dietary patterns of pregnant women and their partners, and offspring at 3 years that were enroled in the 1990-1991 period in the Czech part of the European Longitudinal Study of Pregnancy and Childhood. Multivariable linear regression models were used to estimate the relationship between the dietary patterns of parents (835 child-mother-father trios) during pregnancy and the length/height-for-age z-score of their offspring at birth, 3 years and 19 years. RESULTS: The maternal health-conscious food pattern was found to predict lower child height at 3 years, but not at birth nor at 19 years of age. An increase in the health-conscious pattern score of the maternal diet was associated with significantly lower height-for-age z-score at 3 years; however, the observed effect lost its significance after the adjustment for diet of the child at 3 years. CONCLUSIONS: After full adjustment, the only significant predictors of the height-for-age z-score of the child at 3 years were the heights of both parents and maternal education. More research into the association of maternal diet in pregnancy and height of child is necessary.European Journal of Clinical Nutrition advance online publication, 8 February 2017; doi:10.1038/ejcn.2016.244
On the character of states near the Fermi level in (Ga,Mn)As: impurity to valence band crossover
We discuss the character of states near the Fermi level in Mn doped GaAs, as
revealed by a survey of dc transport and optical studies over a wide range of
Mn concentrations. A thermally activated valence band contribution to dc
transport, a mid-infrared peak at energy hbar omega approx 200 meV in the ac-
conductivity, and the hot photoluminescence spectra indicate the presence of an
impurity band in low doped (<<1% Mn) insulating GaAs:Mn materials. Consistent
with the implications of this picture, both the impurity band ionization energy
inferred from the dc transport and the position of the mid-infrared peak move
to lower energies and the peak broadens with increasing Mn concentration. In
metallic materials with > 2% doping, no traces of Mn-related activated
contribution can be identified in dc-transport, suggesting that the impurity
band has merged with the valence band. No discrepancies with this perception
are found when analyzing optical measurements in the high-doped GaAs:Mn. A
higher energy (hbar omega approx 250 meV) mid-infrared feature which appears in
the metallic samples is associated with inter-valence band transitions. Its
red-shift with increased doping can be interpreted as a consequence of
increased screening which narrows the localized-state valence-band tails and
weakens higher energy transition amplitudes. Our examination of the dc and ac
transport characteristics of GaAs:Mn is accompanied by comparisons with its
shallow acceptor counterparts, confirming the disordered valence band picture
of high-doped metallic GaAs:Mn material.Comment: 10 pages, 12 figure
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