823 research outputs found
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
Alterations in Multiple Measures of White Matter Integrity in Normal Women at High Risk for Alzheimer\u27s Disease
There is evidence that disruption of white matter (WM) microstructure is an early event in the course of Alzheimer\u27s disease (AD). However, the neurobiological bases of WM microstructural declines in presymptomatic AD are unknown. In the present study we address this issue using a multimodal imaging approach to the study of presymptomatic AD. Participants were 37 high-risk (both family history of dementia and one or more APOE4 alleles) women and 20 low-risk (neither family history nor APOE4) women. Groups were matched for age, education, neuropsychological performance, and vascular factors that could affect white matter. Whole-brain analyses of diffusion tensor imaging data [including fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (DA) and radial diffusivity (DR)] and volumetric comparisons of medial temporal lobe (MTL) structures were conducted. Results indicated equivalent entorhinal cortex and hippocampal volumes between risk groups. Nevertheless, the high risk group showed decreased microstructural integrity in WM tracts with direct and secondary connections to the MTL. The predominant alteration in WM integrity in the high AD-risk group was decreased FA not solely driven by either DA or DR changes alone in regions where no MD changes were observed. A second pattern observed in a smaller number of regions involved decreased FA and increased DR. These results suggest that disconnection of MTL-neocortical fiber pathways represents a very early event in the course of AD and suggest that demyelination may represent one contributing mechanism
The Fermi Surface Effect on Magnetic Interlayer Coupling
The oscillating magnetic interlayer coupling of Fe over spacer layers
consisting of CuPd alloys is investigated by first principles
density functional theory. The amplitude, period and phase of the coupling, as
well as the disorder-induced decay, are analyzed in detail and the consistency
to the Ruderman-Kittel-Kasuya-Yoshida (RKKY) theory is discussed. For the first
time an effect of the Fermi surface nesting strength on the amplitude is
established from first principles calculations. An unexpected variation of the
phase and disorder-induced decay is obtained and the results are discussed in
terms of asymptotics
In Situ Detection of Active Edge Sites in Single-Layer MoS Catalysts
MoS2 nanoparticles are proven catalysts for processes such as
hydrodesulphurization and hydrogen evolution, but unravelling their
atomic-scale structure under catalytic working conditions has remained
significantly challenging. Ambient pressure X-ray Photoelectron Spectroscopy
(AP-XPS) allows us to follow in-situ the formation of the catalytically
relevant MoS2 edge sites in their active state. The XPS fingerprint is
described by independent contributions to the Mo3d core level spectrum whose
relative intensity is sensitive to the thermodynamic conditions. Density
Functional Theory (DFT) is used to model the triangular MoS2 particles on
Au(111) and identify the particular sulphidation state of the edge sites. A
consistent picture emerges in which the core level shifts for the edge Mo atoms
evolve counter-intuitively towards higher binding energies when the active
edges are reduced. The shift is explained by a surprising alteration in the
metallic character of the edge sites, which is a distinct spectroscopic
signature of the MoS2 edges under working conditions
Experimental demonstration of a Hadamard gate for coherent state qubits
We discuss and experimentally demonstrate a probabilistic Hadamard gate for
coherent state qubits. The scheme is based on linear optical components,
non-classical resources and the joint projective action of a photon counter and
a homodyne detector. We experimentally characterize the gate for the coherent
states of the computational basis by full tomographic reconstruction of the
transformed output states. Based on the parameters of the experiment we
simulate the fidelity for all coherent state qubits on the Bloch sphere
The social gradient in stress and depressive symptoms among adolescent girls: A systematic review and narrative synthesis
Aim: Socioeconomic inequality is found to negatively influence mental health, but studies investigating the relationship between socioeconomic status (SES) and specific common mental health problems such as stress and depressive symptoms in the general adolescent population are needed. Moreover, gender gaps in mental health among adolescents are evident, but there is a lack of studies that investigate socioeconomic differences in mental health within genders. As girls report consistently more depressive symptoms than do boys, this systematic review specifically investigates whether socioeconomic status is associated with stress and depressive symptoms among adolescent girls in the general population.
Methods: Eligible studies according to predefined inclusion criteria were identified from Medline, PsycINFO, ISI Web of Science, Svemed+ and Idunn. Eight studies were identified, whereby only two measured stress; hence, the evidence base for stress was too limited to perform an analysis. A narrative synthesis was conducted of the six studies that measured depressive symptoms.
Results: A significant inverse social gradient in depressive symptoms among adolescent girls was revealed in all studies that applied parental employment status and perceived financial difficulties as SES measures, while parental educational level and Family Affluence Scale (FAS) gave inconsistent results. The relatively low number of studies may limit interpretation.
Conclusions: Depressive symptoms were more common among adolescent girls with low SES compared to girls with higher SES. SES measures should be applied with care in studies of populations of adolescent girls, as the results can vary based on the chosen indicator. Actions to reduce depressive symptoms among adolescent girls in the general population should include targeting socioeconomic inequalities
Model-based control algorithms for the quadruple tank system: An experimental comparison
We compare the performance of proportional-integral-derivative (PID) control,
linear model predictive control (LMPC), and nonlinear model predictive control
(NMPC) for a physical setup of the quadruple tank system (QTS). We estimate the
parameters in a continuous-discrete time stochastic nonlinear model for the QTS
using a prediction-error-method based on the measured process data and a
maximum likelihood (ML) criterion. In the NMPC algorithm, we use this
identified continuous-discrete time stochastic nonlinear model. The LMPC
algorithm is based on a linearization of this nonlinear model. We tune the PID
controller using Skogestad's IMC tuning rules using a transfer function
representation of the linearized model. Norms of the observed tracking errors
and the rate of change of the manipulated variables are used to compare the
performance of the control algorithms. The LMPC and NMPC perform better than
the PID controller for a predefined time-varying setpoint trajectory. The LMPC
and NMPC algorithms have similar performance.Comment: 6 pages, 5 figures, 3 tables, to be published in Foundations of
Computer Aided Process Operations / Chemical Process Control (FOCAPO/CPC
2023). Hilton San Antonio Hill Country, San Antonio, Texa
Tumor–associated antigens identified by mRNA expression profiling as tumor rejection epitopes
Thirteen H-2(b)-binding peptides derived from six potentially overexpressed proteins in p53(-/- )thymoma (SM7) cells were studied for immunogenecity and vaccine-induced prevention of tumor growth in mice inoculated with SM7 tumor cells. Six of the peptides generated specific CTL responses after immunization, but only two of these peptides (RAD(23–31 )and RAD(24–31)) were capable of generating a weak vaccination-induced protection against adoptive tumor growth. SM7 inoculated mice treated with a blocking antibody against the inhibitory T cell signal transducing molecule CTLA4 appeared to delay tumor take, suggesting that SM7 thymoma cells are recognized by the adaptive immune system of the host. However, prophylactic vaccination with RAD(23–31 )and RAD(24–31 )peptides combined with anti-CTLA4 Ab treatment and did not improve tumor resistance. Our data would indicate that vaccination with immunogenic peptides derived from potentially overexpressed tumor proteins, as identified by mRNA expression profiling of p53(-/- )thymoma cells, at best results in a weak tumor protection thus questioning this way of detection of new tumor rejection epitopes
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