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Correct Choice (correct + choice)
Selected AbstractsTraveltime computation by wavefront-orientated ray tracingGEOPHYSICAL PROSPECTING, Issue 1 2005Radu Coman ABSTRACT For multivalued traveltime computation on dense grids, we propose a wavefront-orientated ray-tracing (WRT) technique. At the source, we start with a few rays which are propagated stepwise through a smooth two-dimensional (2D) velocity model. The ray field is examined at wavefronts and a new ray might be inserted between two adjacent rays if one of the following criteria is satisfied: (1) the distance between the two rays is larger than a predefined threshold; (2) the difference in wavefront curvature between the rays is larger than a predefined threshold; (3) the adjacent rays intersect. The last two criteria may lead to oversampling by rays in caustic regions. To avoid this oversampling, we do not insert a ray if the distance between adjacent rays is smaller than a predefined threshold. We insert the new ray by tracing it from the source. This approach leads to an improved accuracy compared with the insertion of a new ray by interpolation, which is the method usually applied in wavefront construction. The traveltimes computed along the rays are used for the estimation of traveltimes on a rectangular grid. This estimation is carried out within a region bounded by adjacent wavefronts and rays. As for the insertion criterion, we consider the wavefront curvature and extrapolate the traveltimes, up to the second order, from the intersection points between rays and wavefronts to a gridpoint. The extrapolated values are weighted with respect to the distances to wavefronts and rays. Because dynamic ray tracing is not applied, we approximate the wavefront curvature at a given point using the slowness vector at this point and an adjacent point on the same wavefront. The efficiency of the WRT technique is strongly dependent on the input parameters which control the wavefront and ray densities. On the basis of traveltimes computed in a smoothed Marmousi model, we analyse these dependences and suggest some rules for a correct choice of input parameters. With suitable input parameters, the WRT technique allows an accurate traveltime computation using a small number of rays and wavefronts. [source] Dissociating hippocampal subregions: A double dissociation between dentate gyrus and CA1HIPPOCAMPUS, Issue 6 2001Paul E. Gilbert Abstract This study presents a double dissociation between the dentate gyrus (DG) and CA1. Rats with either DG or CA1 lesions were tested on tasks requiring either spatial or spatial temporal order pattern separation. To assess spatial pattern separation, rats were trained to displace an object which covered a baited food-well. The rats were then allowed to choose between two identical objects: one covered the same well as the sample phase object (correct choice), and a second object covered a different unbaited well (incorrect choice). Spatial separations of 15,105 cm were used to separate the correct object from the incorrect object. To assess spatial temporal order pattern separation, rats were allowed to visit each arm of a radial eight-arm maze once in a randomly determined sequence. The rats were then presented with two arms and were required to choose the arm which occurred earliest in the sequence. The choice arms varied according to temporal separation (0, 2, 4, or 6) or the number of arms that occurred between the two choice arms in the sample phase sequence. On each task, once a preoperative criterion was reached, each rat was given either a DG, CA1, or control lesion and then retested. The results demonstrated that DG lesions resulted in a deficit on the spatial task but not the temporal task. In contrast, CA1 lesions resulted in a deficit on the temporal task but not the spatial task. Results suggest that the DG supports spatial pattern separation, whereas CA1 supports temporal pattern separation. Hippocampus 2001;11:626,636. © 2001 Wiley-Liss, Inc. [source] Multilevel generalized linear models for modelling age-related gender difference in violent behaviour and associated factors in the general household populationINTERNATIONAL JOURNAL OF METHODS IN PSYCHIATRIC RESEARCH, Issue 3 2005Min Yang Senior Statistician Abstract It is preferable to use longitudinal data when studying patterns of violence and antisocial behaviour over the lifespan together with the associated risk factors in the general population. From the statistical modelling perspective, random samples of cross-sectional data, representative of the population, can be a reliable alternative. Sampling, weighting, and possible geographical clustering of the behaviour must be considered in the analysis together with correct choice of model as a function of age, although cohort effects and age effects are not separated from the analysis. This paper demonstrates the use of multilevel generalized linear models in the British National Survey of Psychiatric Morbidity in 2000. A multilevel logistic model as a special case of a generalized linear model with individual weightings was adapted for a dichotomous measure of violence and extended to Poisson and negative binomial outcomes. Three types of age function, discrete age effects, continuous age effects, and piecewise polynomial function of age intervals were evaluated for goodness of fit, and for their practical advantages and disadvantages. Models were developed for possible risk factors in relation to specific age groups of interest. Copyright © 2005 John Wiley & Sons, Ltd. Copyright © 2005 John Wiley & Sons, Ltd. [source] Particle Size Distribution (Texture) of Eroded Soil MaterialJOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 5 2002F. Basic Abstract The total quantity of erosional drift on a Stagnic Luvisol on which six tillage methods were used was measured over 5 years of investigation. The texture of the tilled soil and the erosional drift for each trial method was recorded in the same plots. The results obtained suggested that erosional drift was generally richer in silt and clay particles. The standard deviations of coarse sand indicated that approximately the same quantity of coarse sand was found in plot soil and in erosional drift for all tillage methods. Sometimes more and sometimes fewer fine sand particles were found in erosional drift than in plot soil. In most cases, more silt particles were found in erosional drift than in plot soil. The standard deviation and coefficient of variation for clay and silt were higher in erosional drift than in plot soil for all methods. The highest content of clay particles was recorded in erosional drift from the no-tillage treatment in all investigation years. The results suggest that the correct choice of tillage method (no-tillage and ploughing across the slope) on a Stagnic Luvisol can protect the soil on a slope. [source] Search strategies in decision making: the success of "success"JOURNAL OF BEHAVIORAL DECISION MAKING, Issue 2 2004Ben R. Newell Abstract Examination of search strategies has tended to focus on choices determined by decision makers' personal preferences among relevant cues, and not on learning cue-criterion relationships. We present an empirical and rational analysis of cue search for environments with objective criteria. In such environments, cues can be evaluated on the basis of three properties: validity (the probability that a cue identifies the correct choice if cue values differ between alternatives); discrimination rate (the proportion of occasions on which a cue has differing values); and success (the expected proportion of correct choices when only that cue can be used). Our experiments show that though there is a high degree of individual variability, success is a key determinant of search. Furthermore, a rational analysis demonstrates why success-directed search is the most adaptive strategy in many circumstances. Copyright © 2004 John Wiley & Sons, Ltd. [source] Application of genomics to grapevine improvementAUSTRALIAN JOURNAL OF GRAPE AND WINE RESEARCH, Issue 2010G. DI GASPERO Abstract Imagine a breeder browsing a grape chromosome nucleotide-by-nucleotide around a trait locus, scrolling down the list of catalogued genes along a genetic interval, resequencing for a few thousand dollars a potential parent or a selected breeding line. In the past couple of years, this vision has become a reality. The availability of the reference genome sequence has provided significant assistance in the saturation of loci with targeted genetic markers. Grape breeders are now offered unprecedented possibilities for selecting plants using deoxyribonucleic acid (DNA) sequences within or near the gene that controls a desirable trait rather than handling their phenotypes. Genomics-assisted selection offers unique advantages in the correct choice of elite genotypes, in order to improve traits for which limitations of phenotyping technologies or low hereditability adversely affect the efficiency of phenotypic selection. DNA technologies enable the application of marker-assisted selection to thousands of grape seedlings every year, which was previously feasible only for cereals and annuals, enhancing the possibilities of finding an ideal recombinant in populations bred from highly heterozygous parents. The expected outcome is a renewal of the varietal choices available to viticulturists, with novel genotypes that meet the demand for disease-free vines and flavourful grapes. The depth of exploration and characterisation of the existing germplasm is crucial for translating natural diversity into new varieties that could perform beyond the fence of the experimental vineyards and gain substantial market share. We review here how current achievements in genomics and genome sequencing are expected to increase the efficiency of grapevine breeding programs. [source] Development of liquid chromatography/mass spectrometry methods for the quantitative analysis of herbal medicine in biological fluids: a reviewBIOMEDICAL CHROMATOGRAPHY, Issue 1 2010Michael J. Gray Abstract The development of liquid chromatography,mass spectrometry (LC-MS) and tandem MS/MS for the analysis of bioactive components and their metabolites of herbal medicines in biological fluids is reviewed with the aim of providing an overview of the current techniques and methods used. The issues and challenges associated with various stages of the analytical method development are discussed using Ginkgo biloba and Panax ginseng as case studies. LC-MS offers selectivity and specificity in both the chromatographic separation and detection steps. This is necessary in order to measure compounds at extremely low concentrations as is often observed in plasma and urine samples. Traditional methods of detection (UV,visible) do not offer sufficient selectivity and specificity needed. The strategies and pitfalls involved with the measurement of such compounds are discussed in this review. Matrix effects, ,unseen' matrix suppression and enhancement ionization effects can significantly reduce the accuracy and precision of the measurement. The impact of the correct choice of chromatography column formats on signal-to-noise ratio is also discussed. Analytical methods from sample preparation to mass spectrometric detection is outlined in order to provide good direction for analysts intent on the measurement of bioavailable compounds from herbal medicines in plasma and urine samples. Copyright © 2009 John Wiley & Sons, Ltd. [source] Young children who abandon error behaviourally still have to free themselves mentally: a retrospective test for inhibition in intuitive physicsDEVELOPMENTAL SCIENCE, Issue 3 2004Norman H. Freeman When preschoolers overcome persistent error, subsequent patterns of correct choices may identify how the error had been overcome. Children who no longer misrepresented a ball rolling down a bent tube as though it could only fall vertically, were asked sometimes to approach and sometimes to avoid where the ball landed. All children showed requisite task-switching flexibility. The pattern of 4-year-olds' correct choices among different places showed unnecessary avoidance of any place that would previously have tempted them into a vertical-approach error, 5-year-olds rebounded into a reversal, and 7-year-olds were flexible. The data attest to an inhibition mechanism, ruling out competing possibilities. [source] Search strategies in decision making: the success of "success"JOURNAL OF BEHAVIORAL DECISION MAKING, Issue 2 2004Ben R. Newell Abstract Examination of search strategies has tended to focus on choices determined by decision makers' personal preferences among relevant cues, and not on learning cue-criterion relationships. We present an empirical and rational analysis of cue search for environments with objective criteria. In such environments, cues can be evaluated on the basis of three properties: validity (the probability that a cue identifies the correct choice if cue values differ between alternatives); discrimination rate (the proportion of occasions on which a cue has differing values); and success (the expected proportion of correct choices when only that cue can be used). Our experiments show that though there is a high degree of individual variability, success is a key determinant of search. Furthermore, a rational analysis demonstrates why success-directed search is the most adaptive strategy in many circumstances. Copyright © 2004 John Wiley & Sons, Ltd. [source] Features of sequential learning in hemicerebellectomized ratsJOURNAL OF NEUROSCIENCE RESEARCH, Issue 3 2010L. Mandolesi Abstract Because the sequencing property is one of the functions in which cerebellar circuits are involved, it is important to analyze the features of sequential learning in the presence of cerebellar damage. Hemicerebellectomized and control rats were tested in a four-choice visuomotor learning task that required both the detection of a specific sequence of correct choices and the acquisition of procedural rules about how to perform the task. The findings indicate that the presence of the hemicerebellectomy did not affect the first phases of detection and acquisition of the sequential visuomotor task, delayed but did not prevent the learning of the sequential task, slowed down speed-up and proceduralization phases, and loosened the reward-response associative structure. The performances of hemicerebellectomized animals in the serial learning task as well as in the open field task demonstrated that the delayed sequential learning task could not be ascribed to impairment of motor functions or discriminative abilities or to low levels of motivation. The delay in sequential learning observed in the presence of a cerebellar lesion appeared to be related mainly to a delay of the automatization of the response. In conclusion, it may be advanced that, through cortical and subcortical connections, the cerebellum provides the acquisition of rapid and accurate sensory-guided sequence of responses. © 2009 Wiley-Liss, Inc. [source] The effects of verbalization on face recognition in young and older adultsAPPLIED COGNITIVE PSYCHOLOGY, Issue 6 2002Amina Memon To explore the forensic implications of ,verbal overshadowing' in young and older eyewitnesses, we examined the effects of providing a verbal face description on subsequent performance in a lineup task. Young (18,30 years) and older (60,80 years) adults viewed a videotaped crime and performed some unrelated cognitive tasks. Participants in the experimental condition were then asked to supply a description of the target person in the event or to perform a control task. Upon completing the description/control task participants attempted to identify the target person from a target present photo-lineup presented in a sequential or simultaneous mode. Older participants made more false choices and sequential testing reduced correct choices. There was a weak trend consistent with verbal overshadowing that was unrelated to age as well as measures of verbal and face-matching expertise. Although overshadowing reduced performance only slightly, it appeared to affect the self-reported use of a feature-matching strategy linked to accurate decisions by young adults and inaccurate decisions by senior adults. Copyright © 2002 John Wiley & Sons, Ltd. [source] | |||||||||||||||||||