Home About us Contact
|
Home About us Contact | ||
|
|
||
Rapid Acquisition (rapid + acquisition)
Selected AbstractsRapid acquisition of operant conditioning in 5-day-old rat pups: A new technique articulating suckling-related motor activity and milk reinforcementDEVELOPMENTAL PSYCHOBIOLOGY, Issue 6 2007Carlos Arias Abstract Newborn rats are capable of obtaining milk by attaching to a surrogate nipple. During this procedure pups show a gradual increase in head and forelimb movements oriented towards the artificial device that are similar to those observed during nipple attachment. In the present study the probability of execution of these behaviors was analyzed as a function of their contingency with intraoral milk infusion using brief training procedures (15 min). Five-day-old pups were positioned in a smooth surface having access to a touch-sensitive sensor. Physical contact with the sensor activated an infusion pump which served to deliver intraoral milk reinforcement (Paired group). Yoked controls received the reinforcer when Paired neonates touched the sensor. Paired pups trained under a continuous reinforcement schedule emitted significantly more responses than Yoked controls following two (Experiment 1) or one training session (Experiment 2). These differences were also observed during an extinction session conducted immediately after training. The level of maternal deprivation before training (3 or 6 hr) or the volume of milk delivered (1.0 or 1.5 µl per pulse) did not affect acquisition or extinction performances. In addition, it was observed that the rate of responding of Paired pups during the early phase of the extinction session significantly predicted subsequent levels of acceptance of the reinforcer. These results indicate that the frequency of suckling-related behaviors can be rapidly modified by means of associative operant processes. The operant procedure here described represents an alternative tool for the ontogenetic analysis of self-administration or behavior processes of seeking. © 2007 Wiley Periodicals, Inc. Dev Psychobiol 49: 576-588, 2007. [source] A NOVEL PREFERENCE FOR AN INVASIVE PLANT AS A MECHANISM FOR ANIMAL HYBRID SPECIATIONEVOLUTION, Issue 2 2007Dietmar Schwarz Homoploid hybrid speciation,speciation via hybridization without a change in chromosome number,is rarely documented and poorly understood in animals. In particular, the mechanisms by which animal homoploid hybrid species become ecologically and reproductively isolated from their parents are hypothetical and remain largely untested by experiments. For the many host-specific parasites that mate on their host, choosing the right host is the most important ecological and reproductive barrier between these species. One example of a host-specific parasite is the Lonicera fly, a population of tephritid fruit flies that evolved within the last 250 years likely by hybridization between two native Rhagoletis species following a host shift to invasive honeysuckle. We studied the host preference of the Lonicera fly and its putative parent species in laboratory experiments. The Lonicera fly prefers its new host, introduced honeysuckle, over the hosts of both parental species, demonstrating the rapid acquisition of preference for a new host as a means of behavioral isolation from the parent species. The parent taxa discriminate against each other's native hosts, but both accept honeysuckle fruit, leaving the potential for asymmetric gene flow from the parent species. Importantly, this pattern allows us to formulate hypotheses about the initial formation of the Lonicera fly. As mating partners from the two parent taxa are more likely to meet on invasive honeysuckle than on their respective native hosts, independent acceptance of honeysuckle by both parents likely preceded hybridization. We propose that invasive honeysuckle served as a catalyst for the local breakdown of reproductive isolation between the native parent species, a novel consequence of the introduction of an exotic weed. We describe behavioral mechanisms that explain the initial hybridization and subsequent reproductive isolation of the hybrid Lonicera fly. These results provide experimental support for a combination of host shift and hybridization as a model for hybrid speciation in parasitic animals. [source] Individual differences in spatial memory among aged rats are related to hippocampal PKC, immunoreactivityHIPPOCAMPUS, Issue 2 2002Paul J. Colombo Abstract We reported previously that the extent of spatial memory impairment among aged rats was correlated positively with levels of protein kinase C, in hippocampal homogenates measured by quantitative Western blotting (Colombo et al., 1997). In the current study, immunocytochemistry was used to test whether the relationship between elevated PKC, and memory impairment among aged rats could be localized further within regions of the hippocampus. Six- and 24-month-old male Long-Evans rats were first trained in the water maze on a standard place-learning task and then trained 2 weeks later on a transfer task designed for rapid acquisition. In comparison with young rats, aged rats with impaired spatial memory had increased PKC,-immunoreactivity (PKC,-ir) in CA1 of the hippocampus, but not the dentate gyrus. In addition, PKC,-ir in CA1 was correlated positively with spatial memory impairment among aged rats on the standard place-learning and the transfer training tasks. The current results are consistent with our previous report of PKC, in hippocampal homogenates, and show further that the relationships between PKC,-ir and memory impairments among aged rats are most evident in area CA1. Thus age-related impairments of spatial memory, as well as deficits in the flexible use of previously acquired information, may result from dysregulation of PKC,. Hippocampus 2002;12:285,289. © 2002 Wiley-Liss, Inc. [source] Mobile GPS carrier phase tracking using a novel intelligent dual-loop receiverINTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 2 2008Wei-Lung Mao Abstract Carrier phase information is necessary for accurate measurements in global positioning system (GPS) applications. This paper presents a novel intelligent GPS carrier tracking loop with variable-bandwidth characteristics for fast acquisition and better tracking capability in the presence of dynamic environments. Our dual-loop receiver is composed of a frequency-locked loop-assisted phase-locked loop structure, the fuzzy controllers (FCs), and the ATAN discriminator functions. The soft-computing FCs provide the time-varying loop gains to perform accurate and reliable control of the dual-loop paradigm. Once the phase dynamic errors become large under kinematic conditions, the fuzzy loop gains increase adaptively and achieve rapid acquisition. On the other hand, when the tracking errors approach zero in the steady state, the loop gains decrease and the corresponding dual-loop receiver returns to a narrowband system. Four types of carrier phase signals, i.e. phase offset, decaying sinusoidal phase jitter, frequency offset, and frequency ramp offset, are considered to emulate realistic mobile circumstances. Simulation results show that our proposed receiver does achieve a superior performance over conventional tracking loops in terms of faster settling time and wider acquisition range while preventing the occurrence of cycle slips. Copyright © 2008 John Wiley & Sons, Ltd. [source] A high-resolution X-ray diffractometer for the study of imperfect materialsJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 5 2002A. Boulle A high-resolution X-ray diffractometer devoted to the study of imperfect materials (mainly oxides and ceramics) is presented. It is based on a rotating anode generator, a four-bounce monochromator, a five-movement sample holder and a curved position-sensitive detector (PSD). This setup allows rapid acquisition of a reciprocal-space map (in less than 10,h) even for very poorly diffracting materials. The two-dimensional instrumental profile is calculated taking into account each optical element in the beam path. The one-dimensional instrumental profiles corresponding to widely used scans (, scan, ,,2, scan, rocking curve and powder scan) are also calculated. In the three former cases, the setup exhibits an excellent angular resolution (0.003°), whereas in the latter case the resolution is lowered by one order of magnitude at the benefit of a strong increase in the collected intensity. The possibilities of this diffractometer are illustrated with three examples: an epitaxic layer, a microstructured single crystal and a powder. [source] Interactive magnetic resonance cholangiography (MRC) with adaptive averaging,JOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 4 2006Martin J. Graves MSc Abstract Purpose To implement and evaluate a technique for adaptively averaging 2D magnetic resonance cholangiography (MRC) images obtained using an interactive imaging system with a view to improving image quality at reduced fields of view (FOVs). Materials and Methods Images were obtained using an interactive implementation of a single-shot half-Fourier rapid acquisition with relaxation enhancement (RARE) technique. Software was developed for adaptively averaging images, and an evaluation was performed in a phantom and a cohort of 10 patients referred for standard MRC. Adaptively averaged and standard single-shot MRC images were evaluated with respect to their ability to demonstrate the common bile duct and main left and right intrahepatic duct branches. Results In all patient studies there was no difference in the ability of either the adaptive technique or the standard single-shot method to demonstrate the common bile duct and the main left and right intrahepatic duct branches. However, in seven of the 10 patient studies the adaptive technique provided better visualization of the peripheral bile duct system (P = 0.035; sign test). There was no difference in the diagnostic confidence of the two techniques (P = 0.32, Wilcoxon signed-rank test). Conclusion Adaptive averaging of MRC images obtained using an interactive imaging paradigm significantly improves visualization of peripheral intrahepatic ducts. J. Magn. Reson. Imaging 2006. © 2006 Wiley-Liss, Inc. [source] Magnetic resonance microscopy at 17.6-Tesla on chicken embryos in vitroJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 1 2001Bianca Hogers PhD Abstract The non-destructive nature and the rapid acquisition of a three-dimensional image makes magnetic resonance microscopy (MRM) very attractive and suitable for functional imaging investigations. We explored the use of an ultra high magnetic field for MRM to increase image quality per image acquisition time. Improved image quality was characterized by a better signal-to-noise ratio (SNR), better image contrast, and higher resolution compared to images obtained at lower magnetic field strengths. Fixed chicken embryos at several stages of development were imaged at 7.0-T (300 MHz) and at 17.6-T (750 MHz). Maximum intensity projection resulted in three-dimensional vascular images with ample detail of the embryonic vasculature. We showed that at 750 MHz frequency, an image with approximately three times better SNR can be obtained by T1 -weighting using a standard gadolinium contrast agent, compared to the same measurement at 300 MHz. The image contrast improved by around 20 percent and the contrast-to-noise ratio improved by almost a factor of 3.5. Smaller blood vessels of the vascular system were identified at the high field, which indicates a better image resolution. Thus, ultra high field is beneficial for MRM and opens new areas for functional imaging research, in particular when SNR, resolution, and contrast are limited by acquisition time. J. Magn. Reson. Imaging 2001;14:83,86. © 2001 Wiley-Liss, Inc. [source] The apparent electrical conductivity as a surrogate variable for predicting earthworm abundances in tilled soilsJOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 4 2010Monika Joschko Abstract Noninvasive geophysical methods have a great potential for improving soil-biological studies at field or regional scales: they enable the rapid acquisition of soil information which may help to identify potential habitats for soil biota. A precondition for this application is the existence of close relationships between geophysical measurements and the soil organism of interest. This study was conducted to determine whether field measurements of apparent electrical conductivity (ECa) are related to abundances of earthworms in tilled soils. Relationships between ECa and earthworm populations were investigated along transects at 42 plots under reduced and conventional tillage at a 74 ha field on sandy-loam soil in NE Germany. Relations were analyzed with linear-regression and spatial analysis. The apparent electrical conductivity (ECa) was quantitatively related to earthworm abundances sampled 5 months after the geophysical measurements. No relationship was found, however, in plots under conventional tillage when analyzed separately. If earthworm abundances were known at every other location along the transects and if the state-space approach was used for analysis, the analysis of ECa measurements and earthworm abundances indicated that 50% of the earthworm samples could have been substituted by ECa measurements. Further research is needed to fully evaluate the potential of ECa measurements for predicting earthworm habitats in tilled soil. [source] Facile Fabrication of Pure ,-Fe2O3 Nanoparticles via Forced Hydrolysis Using Microwave-Assisted Esterification and their Sensing PropertyJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2009Yafeng Li In this paper we firstly demonstrate a facile approach for the rapid fabrication of ,-Fe2O3 using microwave-assisted esterification. In situ -generated water leads to the forced hydrolysis of Fe3+. Microwave irradiation greatly promotes the growth of ,-Fe2O3 nanoparticles compared with conventional solvothermal approach, and agitation can assure the obtainment of pure hematite phase. The akaganeite phase is preserved without stirring. The BET specific surface area reaches 83 m2/g although high concentration of FeCl3 is adopted. Our approach can assure the very rapid acquisition of hematite nanoparticles. Electrochemical studies indicate that our product can function as a candidate for high-performance sensor. [source] On the application of a non-CPMG single-shot fast spin-echo sequence to diffusion tensor MRI of the human brainMAGNETIC RESONANCE IN MEDICINE, Issue 1 2002Mark E. Bastin Abstract The strong sensitivity of Carr-Purcell-Meiboom-Gill (CPMG) fast spin-echo (FSE) sequences, such as rapid acquisition with relaxation enhancement (RARE), to the phase of the prepared transverse magnetization means that artifact-free single-shot diffusion-weighted images can currently only be obtained with a 30,50% reduction in the signal-to-noise ratio (SNR). However, this phase sensitivity and signal loss can be addressed in FSE sequences that use quadratic phase modulation of the radiofrequency (RF) refocusing pulses to generate a sustained train of stable echoes. Here the first application of such a non-CPMG single-shot FSE (ssFSE) sequence to diffusion tensor MR imaging (DT-MRI) of the human brain is described. This approach provides high SNR diffusion-weighted images that have little or no susceptibility to poor B0 magnetic field homogeneity and the strong eddy currents typically present in DT-MRI experiments. Magn Reson Med 48:6,14, 2002. © 2002 Wiley-Liss, Inc. [source] Training metric accuracy in distance estimation skill: pictures versus wordsAPPLIED COGNITIVE PSYCHOLOGY, Issue 2 2006Gary L. Allen Training metric accuracy in distance estimation skill for distances up to 300,m was done using three different feedback methods: Direct verbal feedback in the field, indirect visual feedback consisting of presentation of labelled markers in the field, and indirect visual feedback consisting of presentation of labelled markers in pictorial depictions of the field. Results from Experiment 1 showed that all three feedback methods resulted in rapid acquisition of skill in estimating perceived distance from a stationary viewpoint and that the skill transferred to a new field setting. Results from Experiment 2 replicated these results for the estimation of traversed distance along routes. These findings have important implications for the use of pictorial presentations, including virtual reality technology, to train generalizable spatial skills. Copyright © 2006 John Wiley & Sons, Ltd. [source] | |||||||||||||