Distortion product otoacoustic emissions evoked by tone complexes

Distortion product otoacoustic emissions are a manifestation of nonlinear interaction between two or more stimulus components within the cochlea. Most studies employ a two-tone stimulus to evoke them. In this study we used a more complex stimulus, in which one of the primaries of the customary two-tone stimulus was replaced by an irregularly spaced tone complex. We obtained data from Mongolian gerbils, and investigated whether the novel stimulus has added value in terms of measurement efficiency, and whether it allows the derivation of information on cochlear mechanics that cannot be derived from two-tone stimuli

Interaural Correlation Fails to Account for Detection in a Classic Binaural Task: Dynamic ITDs Dominate N0Sπ Detection

Binaural signal detection in an NoSπ task relies on interaural disparities introduced by adding an antiphasic signal to diotic noise. What metric of interaural disparity best predicts performance? Some models use interaural correlation; others differentiate between dynamic interaural time differences (ITDs) and interaural level differences (ILDs) of the effective stimulus. To examine the relative contributions of ITDs and ILDs in binaural detection, we developed a novel signal processing technique that selectively degrades different aspects (potential cues) of binaural stimuli (e.g., only ITDs are scrambled). Degrading a particular cue will affect performance only if that cue is relevant to the binaural processing underlying detection. This selective scrambling technique was applied to the stimuli of a classic N0Sπ task in which the listener had to detect an antiphasic 500-Hz signal in the presence of a diotic wideband noise masker. Data obtained from five listeners showed that (1) selective scrambling of ILDs had little effect on binaural detection, (2) selective scrambling of ITDs significantly degraded detection, and (3) combined scrambling of ILDs and ITDs had the same effect as exclusive scrambling of ITDs. Regarding the question which stimulus properties determine detection, we conclude that for this binaural task (1) dynamic ITDs dominate detection performance, (2) ILDs are largely irrelevant, and (3) interaural correlation of the stimulus is a poor predictor of detection. Two simple stimulus-based models that each reproduce all binaural aspects of the data quite well are described: (1) a single-parameter detection model using ITD variance as detection criterion and (2) a compressive transformation followed by a crosscorrelation analysis. The success of both of these contrasting models shows that our data alone cannot reveal the mechanisms underlying the dominance of ITD cues. The physiological implications of our findings are discussed

Drohnenbilder zur Untersuchung von Pflanzenwachstum und Nährstoffdynamik

Ein besseres Verständnis der Dynamik hinter der Freisetzung von pflanzenverfügbaren Nährstoffen aus Boden oder organischen Dünger und eine Verbesserung der Nährstoffverwertung von Ackerfrüchten sind zwei wichtige Herausforderungen, um die Produktivität im ökologischem Ackerbau zu erhöhen. Doch diese Prozesse sind stark sowohl von biotischen (z.B. Bodenmikroben) als auch abiotischen (z.B. Temperatur, Niederschlag, Bodenfeuchtigkeit, Bodenstruktur) Faktoren beeinflusst und erschweren effiziente Untersuchungen. Fernbilderkundung-Technologien (remote sensing) haben sich in den letzten Jahren stark weiterentwickelt und bieten heute neue Ansätze und Methoden, um der Ernährungsstatus von Pflanzen sowie die Dynamik des Pflanzenwachstums nicht destruktiv zu untersuchen. In diesem Beitrag wird, anhand ersten Untersuchungen, die Möglichkeit aus Drohnenbilder Pflanzenwachstum-Parameter zu erfassen und das Potential dieser Technik für wissenschaftliche Untersuchungen und agronomische Beratung diskutiert

Dschungel unter den Füßen Unterirdisches Leben bestimmt das Funktionieren von Agrarökosystemen

This work demonstrates that soil biodiversity plays an important role in agroecosystems. The presence of an enriched soil community in large outdoor lysimeters enhanced plant yield and reduced nutrient leaching losses. Moreover, soil biodiversity loss and simplification of soil communities reduced ecosystem multifunctionality. Further analysis revealed that promotion of soil biodiversity and soil ecological engineering can help to reduce the reliance on external inputs and is especially suitable for a transition to organic agriculture. This work points to the need to support soil life for a sustainable agriculture

Leguminosen als Zwischenbegrünung im ökologischen Ackerbau mit konservierender Bodenbearbeitung

In large-plot field trials leguminous cover crops were examined under conservation tillage systems in organic farming conditions for their ability to suppress weeds. Cover crops were directly drilled after wheat harvest into the field. Suitability of cover crop was estimated by assessing their growth, soil coverage, biomass, biomass of weeds, mulch layer and yield of the main crop, which was either maize or sunflower. Fast growing cover crops, which had a high biomass, reduced weed growth most. Any cover crops grown reduced weed biomass significantly compared to the control without cover crop. Effects on the main crops will be determined after harvest in autumn 2010

Die vielen Facetten von Zwischenfrüchten

Several studies indicate that cover crops can be used to enhance agricultural sustainability as they provide numerous ecological services in agro-ecosystems. They protect soil against erosion and nutrient losses and compete weeds. Moreover, legume species fix nitrogen (N) from the atmosphere and contribute to next crop nutrition. Hence, cover crops complement the ecological aims of organic agriculture. We investigated the impact of cover crops in different cropping systems (organic and conventional) and soil tillage intensities (plough, reduced and no-tillage) in various field experiments. Moreover, results from an experimental network, which has investigated the behavior of more than 11 cover crops, is included. Results show that the effects of cover crops were highest under conservation agriculture or organic farming, and decreased with increasing management intensity. The additional N input by legume cover crops increased the N uptake by the succeeding main crops and cover crops enhanced yield in most of the investigated systems. Cover crops also decreased weed abundance during the fallow period and, predominantly under organic reduced tillage, could reduce weed pressure in the succeeding main crop. Innovative cropping systems (e.g. organic or conservation agriculture) combined with ecological management tools, such as cover crops, have great potential to reduce environmental impact and maintain productivity

Energy Flux in the Cochlea: Evidence Against Power Amplification of the Traveling Wave

Traveling waves in the inner ear exhibit an amplitude peak that shifts with frequency. The peaking is commonly believed to rely on motile processes that amplify the wave by inserting energy. We recorded the vibrations at adjacent positions on the basilar membrane in sensitive gerbil cochleae and tested the putative power amplification in two ways. First, we determined the energy flux of the traveling wave at its peak and compared it to the acoustic power entering the ear, thereby obtaining the net cochlear power gain. For soft sounds, the energy flux at the peak was 1 ± 0.6 dB less than the middle ear input power. For more intense sounds, increasingly smaller fractions of the acoustic power actually reached the peak region. Thus, we found no net power amplification of soft sounds and a strong net attenuation of intense sounds. Second, we analyzed local wave propagation on the basilar membrane. We found that the waves slowed down abruptly when approaching their peak, causing an energy densification that quantitatively matched the amplitude peaking, similar to the growth of sea waves approaching the beach. Thus, we found no local power amplification of soft sounds and strong local attenuation of intense sounds. The most parsimonious interpretation of these findings is that cochlear sensitivity is not realized by amplifying acoustic energy, but by spatially focusing it, and that dynamic compression is realized by adjusting the amount of dissipation to sound intensity

The relevance of schizotypal traits for understanding interpersonal functioning in adolescents with psychiatric problems.

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