6,629 research outputs found
Effect of organic, low-input and conventional production systems on yield and diseases in winter barley
The effect of organic, low-input and conventional management practices on barley yield and disease incidence was assessed in field trials over two years. Conventional fertility management (based on mineral fertiliser applications) and conventional crop protection (based on chemosynthetic pesticides) significantly increased the yield of winter barley as compared to organic fertility and crop protection regimes. Severity of leaf blotch (Rhynchosporium secalis) was highest under organic fertility and crop protection management and was correlated inversely with yield. For mildew (Erysiphe graminis), an interaction between fertility management and crop protection was detected. Conventional crop protection reduced severity of the disease, only under conventional fertility management. Under organic fertility management, incidence of mildew was low and application of synthetic pesticides in “low input” production systems had no significant effect on disease severity
N released from organic amendments is affected by soil management history
A ryegrass bioassay was conducted to investigate the effect of soil management history on nitrogen mineralisation from composted manure and pelleted poultry manure. Soils were used from 2 field experiments comparing conventional and organic/low input management systems. When composted manure was added, soils which had received high rates of composted FYM under biodynamic management released a greater amount of nitrogen for plant uptake than those with a history of mineral or fresh manure fertilisation, suggesting that biological preconditioning may result in greater efficiency of composted FYM as a nitrogen source for plants. “Native” N mineralisation was found to be related to total soil N content
Emergency and on-demand health care: modelling a large complex system
This paper describes how system dynamics was used as a central part of a whole-system review of emergency and on-demand health care in Nottingham, England. Based on interviews with 30 key individuals across health and social care, a 'conceptual map' of the system was developed, showing potential patient pathways through the system. This was used to construct a stock-flow model, populated with current activity data, in order to simulate patient flows and to identify system bottle-necks. Without intervention, assuming current trends continue, Nottingham hospitals are unlikely to reach elective admission targets or achieve the government target of 82% bed occupancy. Admissions from general practice had the greatest influence on occupancy rates. Preventing a small number of emergency admissions in elderly patients showed a substantial effect, reducing bed occupancy by 1% per annum over 5 years. Modelling indicated a range of undesirable outcomes associated with continued growth in demand for emergency care, but also considerable potential to intervene to alleviate these problems, in particular by increasing the care options available in the community
Saturated gain spectrum of VECSELs determined by transient measurement of lasing onset
We describe time-resolved measurements of the evolution of the spectrum of radiation emitted by an optically-pumped continuous-wave InGaAs-GaAs quantum well laser, recorded as lasing builds up from noise to steady state. We extract a fitting parameter corresponding to the gain dispersion of the parabolic spectrum equal to ?79 ± 30 fs2 and ?36 ± 6 fs2 for a resonant and anti-resonant structure, respectively. Furthermore the recorded evolution of the spectrum allows for the calculation of an effective FWHM gain bandwidth for each structure, of 11 nm and 18 nm, respectively
ESR modes in a Strong-Leg Ladder in the Tomonaga-Luttinger Liquid Phase
Magnetic excitations in the strong-leg quantum spin ladder compound
(CHN)CuBr (known as DIMPY) in the field-induced
Tomonaga-Luttinger spin liquid phase are studied by means of high-field
electron spin resonance (ESR) spectroscopy. The presence of a gapped ESR mode
with unusual non-linear frequency-field dependence is revealed experimentally.
Using a combination of analytic and exact diagonalization methods, we compute
the dynamical structure factor and identify this mode with longitudinal
excitations in the antisymmetric channel. We argue that these excitations
constitute a fingerprint of the spin dynamics in a strong-leg spin-1/2
Heisenberg antiferromagnetic ladder and owe its ESR observability to the
uniform Dzyaloshinskii-Moriya interaction
The Two-Dimensional Square-Lattice S=1/2 Antiferromagnet Cu(pz)(ClO)
We present an experimental study of the two-dimensional S=1/2 square-lattice
antiferromagnet Cu(pz)(ClO) (pz denotes pyrazine - )
using specific heat measurements, neutron diffraction and cold-neutron
spectroscopy. The magnetic field dependence of the magnetic ordering
temperature was determined from specific heat measurements for fields
perpendicular and parallel to the square-lattice planes, showing identical
field-temperature phase diagrams. This suggest that spin anisotropies in
Cu(pz)(ClO) are small. The ordered antiferromagnetic structure is a
collinear arrangement with the magnetic moments along either the
crystallographic b- or c-axis. The estimated ordered magnetic moment at zero
field is m_0=0.47(5)mu_B and thus much smaller than the available single-ion
magnetic moment. This is evidence for strong quantum fluctuations in the
ordered magnetic phase of Cu(pz)(ClO). Magnetic fields applied
perpendicular to the square-lattice planes lead to an increase of the
antiferromagnetically ordered moment to m_0=0.93(5)mu_B at mu_0H=13.5T -
evidence that magnetic fields quench quantum fluctuations. Neutron spectroscopy
reveals the presence of a gapped spin excitations at the antiferromagnetic zone
center, and it can be explained with a slightly anisotropic nearest neighbor
exchange coupling described by J_1^{xy}=1.563(13)meV and
J_1^z=0.9979(2)J_1^{xy}
Quantum critical dynamics of a S = 1/2 antiferromagnetic Heisenberg chain studied by 13C-NMR spectroscopy
We present a 13C-NMR study of the magnetic field driven transition to
complete polarization of the S=1/2 antiferromagnetic Heisenberg chain system
copper pyrazine dinitrate Cu(C_4H_4N_2)(NO_3)_2 (CuPzN). The static local
magnetization as well as the low-frequency spin dynamics, probed via the
nuclear spin-lattice relaxation rate 1/T_1, were explored from the low to the
high field limit and at temperatures from the quantum regime (k_B T << J) up to
the classical regime (k_B T >> J). The experimental data show very good
agreement with quantum Monte Carlo calculations over the complete range of
parameters investigated. Close to the critical field, as derived from static
experiments, a pronounced maximum in 1/T_1 is found which we interpret as the
finite-temperature manifestation of a diverging density of zero-energy magnetic
excitations at the field-driven quantum critical point.Comment: 5 pages, 4 figure
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