24,580 research outputs found
Comparative review of the effects of organic farming on biodiversity (OF0149)
This is the final report of Defra project OF0149
1. The report reviews the impact of different farming regimes and makes a comparative study of their influence on the biodiversity of arable farmland.
2. Within this review, the evaluation of impacts on biodiversity focuses on species and habitats, and includes both the number, abundance and activity of species (section 1.3).
3. Five farming regimes are defined and discussed, namely Conventional Arable, Conventional Mixed Lowland, Organic and two integrated production regimes - LEAF (Linking Environment and Farming) and IFS-Experimental regimes The main differences between the regimes in relation to the use of external inputs and other agricultural practices are discussed. The review draws on both UK and European information (section 1.4).
4. The effect of each farming regime on biodiversity is assessed according to the agricultural practices adopted and to the occurrence and management of uncropped land present. Agricultural practices are reviewed within the following categories: cultivation, crop production, crop protection and post-cropping practice (section 2.1).
5. Among the agricultural practices examined, those associated with crop protection and the artificial inputs associated with crop production were seen as the most adverse for biodiversity. Several practices were seen to benefit the biodiversity of arable land. These included set-aside, crop rotations with grass leys, spring sowing, permanent pasture, green manuring and intercropping (section 2.7).
6. Uncropped areas, such as sown grass strips (beetle banks), grass margins and conservation headlands, were seen as critical for the maintenance of biodiversity on arable farmland. Changes in the balance of cropped to uncropped land within some farming regimes, linked to increase in field size, have had a major impact on the diversity of flora and fauna associated with those regimes (section 3.4).
7. Based on the evaluation of agricultural practices used, the occurrence of uncropped land and the extent of the farming regime within England and Wales, it was concluded that Conventional Arable regimes act effectively to maintain the impoverished status of biodiversity on arable land. Extreme examples can be found of intensively managed farms that further deplete biodiversity and sympathetically managed farms that try to enhance it. Increased adoption of agricultural practices such as direct drilling, use of farmyard manure, set-aside, use of crop rotations with leys, or an increase in the incidence and sympathetic management of uncropped areas may well assist biodiversity on farms within this regime (sections 4.3 & 4.4)
8. Organic regimes were shown to have an overall benefit for biodiversity at the farm level, both in terms of the agricultural practices adopted and in the occurrence and management of uncropped areas (sections 4.3 & 4.4).
9. Conventional Mixed Lowland and LEAF regimes were both seen to have the potential for enhancing biodiversity on arable land. Here, adverse impacts associated with crop protection and crop production may be mitigated by beneficial effects associated with post-cropping practices, the occurrence of permanent pasture and uncropped land. At present, the extent to which enhancement may be achieved, may well depend on the extent, condition and management of uncropped land present within these regimes (sections 4.3 & 4.4).
10. IFS-experimental regimes were seen to have a beneficial effect on biodiversity, due to the stringent procedures used for targeting herbicides and pesticides and for establishing and managing uncropped areas. At present these regimes occupy a tiny area of the national resource of arable land and thus their impact on national biodiversity is likely to be insignificant at the present time (sections 4.3 & 4.4).
11. A number of areas are highlighted for further consideration. These include:
• monitoring of biodiversity on farms pre- and post- conversion to organic farming,
• comparative studies that focus on the effectiveness of different regimes or agricultural practices in enhancing biodiversity on species-impoverished intensively managed arable land,
• manipulative experiments to determine the optimal balance of cropped to uncropped areas for enhancing biodiversity,
• manipulative experiments to examine the separate impacts of rotational regimes and agricultural inputs on biodiversity,
• an economic assessment of the costs and benefits in both production and biodiversity terms, of conversion to organic, integrated production or uptake of available agri-environment schemes
Spin-exchange relaxation free magnetometry with Cs vapor
We describe a Cs atomic magnetometer operating in the spin-exchange
relaxation-free (SERF) regime. With a vapor cell temperature of
we achieve intrinsic magnetic resonance widths corresponding to an electron spin-relaxation rate of when the spin-exchange rate is . We
also observe an interesting narrowing effect due to diffusion. Signal-to-noise
measurements yield a sensitivity of about .
Based on photon shot noise, we project a sensitivity of . A theoretical optimization of the magnetometer indicates
sensitivities on the order of should be achievable in a
volume. Because Cs has a higher saturated vapor pressure than
other alkali metals, SERF magnetometers using Cs atoms are particularly
attractive in applications requiring lower temperatures.Comment: 8 pages, 6 figures. submitted to PR
Correlations between hidden units in multilayer neural networks and replica symmetry breaking
We consider feed-forward neural networks with one hidden layer, tree
architecture and a fixed hidden-to-output Boolean function. Focusing on the
saturation limit of the storage problem the influence of replica symmetry
breaking on the distribution of local fields at the hidden units is
investigated. These field distributions determine the probability for finding a
specific activation pattern of the hidden units as well as the corresponding
correlation coefficients and therefore quantify the division of labor among the
hidden units. We find that although modifying the storage capacity and the
distribution of local fields markedly replica symmetry breaking has only a
minor effect on the correlation coefficients. Detailed numerical results are
provided for the PARITY, COMMITTEE and AND machines with K=3 hidden units and
nonoverlapping receptive fields.Comment: 9 pages, 3 figures, RevTex, accepted for publication in Phys. Rev.
Magic numbers in the discrete tomography of cyclotomic model sets
We report recent progress in the problem of distinguishing convex subsets of
cyclotomic model sets by (discrete parallel) X-rays in prescribed
-directions. It turns out that for any of these model sets
there exists a `magic number' such that any two
convex subsets of can be distinguished by their X-rays in any set
of prescribed -directions. In particular, for
pentagonal, octagonal, decagonal and dodecagonal model sets, the least possible
numbers are in that very order 11, 9, 11 and 13.Comment: 6 pages, 1 figure; based on the results of arXiv:1101.4149 [math.MG];
presented at Aperiodic 2012 (Cairns, Australia
Statistical mechanics of the multi-constraint continuous knapsack problem
We apply the replica analysis established by Gardner to the multi-constraint
continuous knapsack problem,which is one of the linear programming problems and
a most fundamental problem in the field of operations research (OR). For a
large problem size, we analyse the space of solution and its volume, and
estimate the optimal number of items to go into the knapsack as a function of
the number of constraints. We study the stability of the replica symmetric (RS)
solution and find that the RS calculation cannot estimate the optimal number of
items in knapsack correctly if many constraints are required.In order to obtain
a consistent solution in the RS region,we try the zero entropy approximation
for this continuous solution space and get a stable solution within the RS
ansatz.On the other hand, in replica symmetry breaking (RSB) region, the one
step RSB solution is found by Parisi's scheme. It turns out that this problem
is closely related to the problem of optimal storage capacity and of
generalization by maximum stability rule of a spherical perceptron.Comment: Latex 13 pages using IOP style file, 5 figure
Instrumentation for Computerized Heart Catheterization
journal articleBiomedical Informatic
Standardized Coding of the Medical Problem List (Letter)
journal articleBiomedical Informatic
Integration of a Stand-Alone Expert System with a Hospital Information System
Conference PaperBiomedical Informatic
Optimizing the Electrocardiogram and Pressure Monitoring
journal articleBiomedical Informatic
A canonical ensemble approach to graded-response perceptrons
Perceptrons with graded input-output relations and a limited output precision
are studied within the Gardner-Derrida canonical ensemble approach. Soft non-
negative error measures are introduced allowing for extended retrieval
properties. In particular, the performance of these systems for a linear and
quadratic error measure, corresponding to the perceptron respectively the
adaline learning algorithm, is compared with the performance for a rigid error
measure, simply counting the number of errors. Replica-symmetry-breaking
effects are evaluated.Comment: 26 pages, 10 ps figure
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