Utilising intrinsic robustness in agricultural production systems: Inventions for a sustainable development of agriculture

This paper explores the potential of utilising robust crops and livestock for improving sustainability of agriculture. Two approaches for dealing with unwanted fluctuations that may influence agricultural production, such as diseases and pests, are discussed. The prevailing approach, which we call the ‘Control Model’, is to protect crops and livestock from disturbances as much as possible, to regain balance with monitoring and intervention and to look for add-on solutions only. There are a number of problems associated with the Control Model, including reduced animal welfare, environmental pollution and low public support. An alternative approach, which we call the ‘Adaptation Model’, is based on reducing the consequences of disturbances rather than taking disturbances ou

A statistical approach to the problem of negatives in input-output analysis

Models;econometrics

A superconducting modulator for extremely sensitive voltage measurements across multifilamentary superconducting wires

In this paper we describe a superconducting chopper amplifier used as an instrument to measure the V(I) curve of multifilamentary superconductors. Experimental results are presented

Spread of epileptiform activity in the immature rat neocortex studied with voltage-sensitive dyes and laser scanning microscopy

1. Adult rats and rats with a postnatal age of 3-29 days (PN 3-29) were used for the preparation of in vitro slices of the frontal neocortex. Epileptiform activity was induced by bath application of the gamma-aminobutyric acid-A (GABAA) receptor antagonists bicuculline or picrotoxin. 2. The voltage-sensitive dye RH 414 and a laser scanning microscope were used for multiple-site optical recordings of membrane potential changes associated with epileptiform activity. Optical signals were compared with simultaneously measured extra-cellular field potentials. 3. Optical signals could be reliably recorded for the duration of the experiments (2-4 h). Extracellular recordings of convulsant-induced paroxysmal depolarizing shifts (PDSs) in slices stained with RH 414 were comparable with those obtained in unstained slices. Changes in dye signals in response to reductions in extracellular calcium, addition of tetrodotoxin (TTX), or application of excitatory amino acid receptor antagonists indicate that the fluorescence changes correlate well with established electrophysiological measures of epileptiform activity. 4. In slices from adult animals, dye signals were observed at all recording sites. The response with the shortest latency occurred invariably at the site of stimulation, and activity spread rapidly in both vertical and horizontal directions. Spread was significantly faster in the vertical than in the horizontal direction. 5. Epileptiform activity was absent or only weakly expressed in slices from PN 3-9 animals. Activity was detectable predominantly in upper cortical layers. 6. Dye signals were observed at all measurement points in slices from PN 10-19 animals. In this age group, peak amplitude increased with spread of activity from lower to upper cortical layers. There was no significant difference between the speed of propagation in the vertical and in the horizontal directions. Spontaneous epileptiform activity occurred at a high rate in the PN 10-19 age group, and signals associated with spontaneous epileptiform events were largest in upper layers. 7. In the PN 10-19 age group, optical signals were characterized by the repetitive occurrence of PDS discharges superimposed on a sustained response. The amplitude of the sustained response decreased with increasing distance from the site of stimulation. Analysis of the latencies revealed that the superimposed PDS-like events were generated at multiple sites within the scanning area. Amplitude and rate of rise were largest in slices from PN 10-19 animals. These values declined with ongoing development

Screening and characterization of Lactobacillus strains producing large amounts of exopolysaccharides

A total of 182 Lactobacillus strains were screened for production of extracellular polysaccharides (EPS) by a new method: growth in liquid media with high sugar concentrations. Sixty EPS-positive strains were identified; 17 strains produced more than 100 mg/l soluble EPS. Sucrose was an excellent substrate for abundant EPS synthesis. The ability to produce glucans appears to be widespread in the genus Lactobacillus. The monosaccharide composition of EPS produced by Lactobacillus reuteri strain LB 121 varied with the growth conditions (solid compared to liquid medium) and the sugar substrates (sucrose or raffinose) supplied in the medium. Strain LB 121 produced both a glucan and a fructan on sucrose, but only a fructan on raffinose. This is the first report of fructan production by a Lactobacillus species. EPS production increased with increasing sucrose concentrations and involved extracellular sucrase-type enzymes.

Fixed-Node Monte Carlo Calculations for the 1d Kondo Lattice Model

The effectiveness of the recently developed Fixed-Node Quantum Monte Carlo method for lattice fermions, developed by van Leeuwen and co-workers, is tested by applying it to the 1D Kondo lattice, an example of a one-dimensional model with a sign problem. The principles of this method and its implementation for the Kondo Lattice Model are discussed in detail. We compare the fixed-node upper bound for the ground state energy at half filling with exact-diagonalization results from the literature, and determine several spin correlation functions. Our `best estimates' for the ground state correlation functions do not depend sensitively on the input trial wave function of the fixed-node projection, and are reasonably close to the exact values. We also calculate the spin gap of the model with the Fixed-Node Monte Carlo method. For this it is necessary to use a many-Slater-determinant trial state. The lowest-energy spin excitation is a running spin soliton with wave number pi, in agreement with earlier calculations.Comment: 19 pages, revtex, contribution to Festschrift for Hans van Leeuwe

Relating alpha power modulations to competing visuospatial attention theories

Visuospatial attention theories often propose hemispheric asymmetries underlying the control of attention. In general support of these theories, previous EEG/MEG studies have shown that spatial attention is associated with hemispheric modulation of posterior alpha power (gating by inhibition). However, since measures of alpha power are typically expressed as lateralization scores, or collapsed across left and right attention shifts, the individual hemispheric contribution to the attentional control mechanism remains unclear. This is, however, the most crucial and decisive aspect in which the currently competing attention theories continue to disagree. To resolve this long-standing conflict, we derived predictions regarding alpha power modulations from Heilman's hemispatial theory and Kinsbourne's interhemispheric competition theory and tested them empirically in an EEG experiment. We used an attention paradigm capable of isolating alpha power modulation in two attentional states, namely attentional bias in a neutral cue condition and spatial orienting following directional cues. Differential alpha modulations were found for both hemispheres across conditions. When anticipating peripheral visual targets without preceding directional cues (neutral condition), posterior alpha power in the left hemisphere was generally lower and more strongly modulated than in the right hemisphere, in line with the interhemispheric competition theory. Intriguingly, however, while alpha power in the right hemisphere was modulated by both, cue-directed leftward and rightward attention shifts, the left hemisphere only showed modulations by rightward shifts of spatial attention, in line with the hemispatial theory. This suggests that the two theories may not be mutually exclusive, but rather apply to different attentional states

Left parietal tACS at alpha frequency induces a shift of visuospatial attention

Background Voluntary shifts of visuospatial attention are associated with a lateralization of parieto-occipital alpha power (7-13Hz), i.e. higher power in the hemisphere ipsilateral and lower power contralateral to the locus of attention. Recent noninvasive neuromodulation studies demonstrated that alpha power can be experimentally increased using transcranial alternating current stimulation (tACS). Objective/Hypothesis We hypothesized that tACS at alpha frequency over the left parietal cortex induces shifts of attention to the left hemifield. However, spatial attention shifts not only occur voluntarily (endogenous/ top-down), but also stimulus-driven (exogenous/ bottom-up). To study the task-specificity of the potential effects of tACS on attentional processes, we administered three conceptually different spatial attention tasks. Methods 36 healthy volunteers were recruited from an academic environment. In two separate sessions, we applied either high-density tACS at 10Hz, or sham tACS, for 35–40 minutes to their left parietal cortex. We systematically compared performance on endogenous attention, exogenous attention, and stimulus detection tasks. Results In the endogenous attention task, a greater leftward bias in reaction times was induced during left parietal 10Hz tACS as compared to sham. There were no stimulation effects in either the exogenous attention or the stimulus detection task. Conclusion The study demonstrates that high-density tACS at 10Hz can be used to modulate visuospatial attention performance. The tACS effect is task-specific, indicating that not all forms of attention are equally susceptible to the stimulation