Saccadic target selection as a function of time.

Recent evidence indicates that stimulus-driven and goal-directed control of visual selection operate independently and in different time windows (van Zoest et al., 2004). The present study further investigates how eye movements are affected by stimulus-driven and goal-directed control. Observers were presented with search displays consisting of one target, multiple non-targets and one distractor element. The task of observers was to make a fast eye movement to a target immediately following the offset of a central fixation point, an event that either co-occurred with or soon followed the presentation of the search display. Distractor saliency and target-distractor similarity were independently manipulated. The results demonstrated that the effect of distractor saliency was transient and only present for the fastest eye movements, whereas the effect of target-distractor similarity was sustained and present in all but the fastest eye movements. The results support an independent timing account of visual selection. © VSP 2006

Goal-driven modulations as a function of time in saccadic target selection

Four experiments were performed to investigate the contribution of goal-driven modulation in saccadic target selection as a function of time. Observers were required to make an eye movement to a prespecified target that was concurrently presented with multiple nontargets and possibly one distractor. Target and distractor were defined in different dimensions (orientation dimension and colour dimension in Experiment 1), or were both defined in the same dimension (i.e., both defined in the orientation dimension in Experiment 2, or both defined in the colour dimension in Experiments 3 and 4). The identities of target and distractor were switched over conditions. Speed-accuracy functions were computed to examine the full time course of selection in each condition. There were three major results. First, the ability to exert goal-driven control increased as a function of response latency. Second, this ability depended on the specific target-distractor combination, yet was not a function of whether target and distractor were defined within or across dimensions. Third, goal-driven control was available earlier when target and distractor were dissimilar than when they were similar. It was concluded that the influence of goal-driven control in visual selection is not all or none, but is of a continuous nature. © 2007 The Experimental Psychology Society

Stimulus-salience and the timecourse of saccade trajectory deviations

The deviation of a saccade trajectory is a measure of the oculomotor competition evoked by a distractor. The aim of the present study was to investigate the impact of stimulus-salience on the time-course of saccade trajectory deviations to get a better insight into how stimulus-salience influences oculomotor competition over time. Two experiments were performed in which participants were required to make a vertical saccade to a target presented in an array of nontarget line elements and one additional distractor. The distractor varied in salience, where salience was defined by an orientation contrast relative to the surrounding nontargets. In Experiment 2, target-distractor similarity was additionally manipulated. In both Experiments 1 and 2, the results revealed that the eyes deviated towards the irrelevant distractor and did so more when the distractor was salient compared to when it was not salient. Critically, salience influenced performance only when people were fast to elicit an eye movement and had no effect when saccade latencies were long. Target-distractor similarity did not influence this pattern. These results show that the impact of salience in the visual system is transient. © 2012 ARVO

Parasitic chytrids could promote copepod survival by mediating material transfer from inedible diatoms

Diatoms form large spring blooms in lakes and oceans, providing fuel for higher trophic levels at the start of the growing season. Some of the diatom blooms, however, are not grazed by filter-feeding zooplankton like Daphnia due to their large size. Several of these large diatoms are susceptible to chytrid infections. Zoospores of chytrids appeared to be excellent food for Daphnia, both in terms of size, shape, and quality (PUFAs and cholesterol). Thus, zoospores of chytrids can bridge the gap between inedible diatoms and Daphnia. In order to examine the effects of diatoms and chytrids on the survival of copepods, we performed one grazing and one survival experiment. The grazing experiment revealed that the diatom, Asterionella formosa, was not grazed by the copepod, Eudiaptomus gracilis, even after being infected by the chytrid Zygorhizidium planktonicum. However, carbon and nitrogen concentrations were significantly reduced by E. gracilis only when A. formosa was infected by Z. planktonicum, indicating that the chytrids might facilitate material transfer from inedible diatoms to the copepods. The survival experiment revealed that E. gracilis lived shorter with A. formosa than with the cryptophyta Cryptomonas pyrenoidifera. However, the survival of E. gracilis increased significantly in the treatment where A. formosa cells were infected by Z. planktonicum. Since E. gracilis could not graze A. formosa cells due to their large colonial forms, E. gracilis may acquire nutrients by grazing on the zoospores, and were so able to survive in the presence of the A. formosa. This provides new insights into the role of parasitic fungi in aquatic food webs, where chytrids may improve copepod survival during diatom blooms.

Progressive neurological deficits in multiple myeloma: meningeal myelomatosis without MRI abnormalities

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Towards a developmental state? Provincial economic policy in South Africa

This paper explores the meaning of the developmental state for spatial economic policy in South Africa. Two main questions are addressed: do provincial governments have a role to play in promoting economic prosperity, and to what extent do current provincial policies possess the attributes of a developmental state? These attributes are defined as the ability to plan longer term, to focus key partners on a common agenda, and to mobilise state resources to build productive capabilities. The paper argues that the developmental state must harness the power of government at every level to ensure that each part of the country develops to its potential. However, current provincial capacity is uneven, and weakest where support is needed most. Many provinces seem to have partial strategies and lack the wherewithal for sustained implementation. Coordination across government appears to be poor. The paper concludes by suggesting ways provincial policies could be strengthened

Strength demands of tall wind turbines subject to earthquakes and wind load

Wind and earthquake load have historically been conceived to act independently. However, if we reflect on the fact that major seismic events are usually followed by a number of aftershocks and that wind is constantly flowing at high intensities around wind farms, which induces additional demands of resistance to infrastructure, then the joint probability of middle-to strong earthquakes and low-to mild wind events becomes more relevant. In this paper a generalised approach is used to estimate the ratio between earthquake and wind forces and their effect on infrastructure. Following, a probabilistic analysis is carried out to show that under certain conditions the combination of these natural events can induce additional demands of strength and ductility to wind turbines which could lead to unforeseen damage

Resuspensie, sedimentatie en lichtklimaat in de Breukeleveense Plas.

Opwerveling van slib kan in ondiepe Nederlandse oppervlaktewateren een aanzienlijke bijdrage leveren aan de uitdoving van het licht onder water. In 1989 werd gepoogd om door Actief Biologisch Beheer, door verwijdering van een groot deel van de planktivore en benthivore visstand, het doorzicht in de Breukeleveense Bias te vergroten. Deze ingreep gaf echter geen verbetering in het onder water lichtklimaat te zien. Als één van de belangrijkste oorzaken voor het uitblijven van succes wordt de door de wind veroorzaakte opwerveling van bodemslib gezien. Deze studie beschrijft het onder water lichtklimaat in de plas. Het onderzoek was gericht op de bijdrage van verschillende componenten en de invloed van wind op de uitdoving van licht en de vermindering van het doorzicht. De extinctiecoëfficiënten en het doorzicht zijn geschat met behulp van het model UITZICHT. Met dit model werd inzicht verkregen in de bijdrage van verschillende componenten aan de extinctie en het doorzicht. In de plas blijken algen (ca. 50%) en detritus (ca. 25%) in hoge mate verantwoordelijk voor de uitdoving van licht. Met het model DYNHX kon worden afgeleid wat de bijdrage van geresuspendeerd bodemslib aan de extinctie en de afname van het doorzicht is. In het slibrijke zuidwesten van de plas is de bijdrage aan de extinctie gemiddeld 25% resulterend in een afname van het doorzicht van gemiddeld 0,44 tot 0,30 m. In het meer zanderige noordoosten is de bijdrage van resuspensie aan de extinctie gemiddeld 17%, het doorzicht wordt hierdoor gereduceerd van gemiddeld 0,41 tot 0,32 m. In perioden met hevige wind kunnen de bijdragen van resuspensie aan de extinctie oplopen tot 72% in het zuidwesten en tot 44°/o in het noordoosten van de plas. Tijdens deze perioden blijkt het doorzicht gereduceerd te worden tot 0,13 m in het zuidwesten en tot 0,22 m in het noordoosten van de plas. Voor een verbetering van het doorzicht zullen naast reductie van de planktivore en benthivore visstand aanvullende maatregelen voor de reductie van de slibopwerveling nodig zijn aangezien baggeren, vanwege de extreem hoge kosten, geen reële oplossing blijkt

Corn residue stocking rate affects cattle performance but not subsequent grain yield

This study investigated effects of stocking rate on cattle performance, quality and quantity of corn residue, and impact of residue removal on grain yield for 5 yr at the University of Nebraska – Lincoln West Central Water Resources Field Laboratory near Brule, NE. Four removal treatments—1) no removal (control), 2) grazing at 2.5 animal unit month (AUM)/ ha, 3) grazing at 5.0 AUM/ha, and 4) baling—were applied to a center pivot–irrigated corn field (53 ha). The field was divided into eight 6.6-ha paddocks to which replicated treatments were assigned. Samples of residue were collected in October and March (before and after residue removal) using ten 0.5-m2 quadrats per treatment replication. Residue was separated into 5 plant parts—stem, cob, leaf, husk, and grain—and analyzed for nutrient content. Esophageally fistulated cattle were used to measure diet quality. Cattle assigned to the 2.5 AUM/ha stocking rate treatment gained more BW (P \u3c 0.01) and BCS (P \u3c 0.01) than cattle assigned to the 5.0 AUM/ha treatment. Leaf contained the most (P \u3c 0.01) CP and husk had the greatest (P \u3c 0.01) in vitro OM disappearance (IVOMD) but the CP and IVOMD of individual plant parts did not differ (P \u3e 0.69) between sampling dates. Amount of total residue was reduced (P \u3c 0.05) by baling and both grazing treatments between October and March but was not different (P \u3e 0.05) in control paddocks between sampling dates. As a proportion of the total residue, stem increased (P \u3c 0.01) and husk decreased (P \u3c 0.01) between October and March. Diet CP content was similar (P = 0.10) between sampling dates for the 2 grazing treatments but IVOMD was greater after grazing in the 2.5 AUM/ha grazing treatment (P = 0.04). Subsequent grain yields were not different (P = 0.16) across all 4 residue removal treatments. At the proper stocking rate, corn residue grazing results in acceptable animal performance without negatively impacting subsequent corn grain production

Corn residue stocking rate affects cattle performance but not subsequent grain yield

This study investigated effects of stocking rate on cattle performance, quality and quantity of corn residue, and impact of residue removal on grain yield for 5 yr at the University of Nebraska – Lincoln West Central Water Resources Field Laboratory near Brule, NE. Four removal treatments—1) no removal (control), 2) grazing at 2.5 animal unit month (AUM)/ ha, 3) grazing at 5.0 AUM/ha, and 4) baling—were applied to a center pivot–irrigated corn field (53 ha). The field was divided into eight 6.6-ha paddocks to which replicated treatments were assigned. Samples of residue were collected in October and March (before and after residue removal) using ten 0.5-m2 quadrats per treatment replication. Residue was separated into 5 plant parts—stem, cob, leaf, husk, and grain—and analyzed for nutrient content. Esophageally fistulated cattle were used to measure diet quality. Cattle assigned to the 2.5 AUM/ha stocking rate treatment gained more BW (P \u3c 0.01) and BCS (P \u3c 0.01) than cattle assigned to the 5.0 AUM/ha treatment. Leaf contained the most (P \u3c 0.01) CP and husk had the greatest (P \u3c 0.01) in vitro OM disappearance (IVOMD) but the CP and IVOMD of individual plant parts did not differ (P \u3e 0.69) between sampling dates. Amount of total residue was reduced (P \u3c 0.05) by baling and both grazing treatments between October and March but was not different (P \u3e 0.05) in control paddocks between sampling dates. As a proportion of the total residue, stem increased (P \u3c 0.01) and husk decreased (P \u3c 0.01) between October and March. Diet CP content was similar (P = 0.10) between sampling dates for the 2 grazing treatments but IVOMD was greater after grazing in the 2.5 AUM/ha grazing treatment (P = 0.04). Subsequent grain yields were not different (P = 0.16) across all 4 residue removal treatments. At the proper stocking rate, corn residue grazing results in acceptable animal performance without negatively impacting subsequent corn grain production