High Temporal (high + temporal)

Distribution by Scientific Domains

Terms modified by High Temporal

  • high temporal resolution

  • Selected Abstracts


    High temporal and spatial resolution 4D MRA using spiral data sampling and sliding window reconstruction

    MAGNETIC RESONANCE IN MEDICINE, Issue 1 2004
    He Zhu
    Abstract Contrast-enhanced magnetic resonance angiography (CE-MRA) requires high spatial resolution to demonstrate detailed vasculature and high temporal resolution to capture the contrast bolus. Sparse bright voxels in MRA permit substantial undersampling in MRI data acquisition, allowing simultaneous high temporal and spatial resolution. We developed a time-resolved 3D MRA technique using the efficient spiral sampling trajectory, and performed off-resonance corrections using inhomogeneity field maps. View sharing and sliding window reconstruction were utilized to generate high temporal resolution. High-resolution 3D angiograms were generated at 1,2 s per frame, with a 5,8 ml gadolinium dose, in patients with vascular disease. Magn Reson Med 52:14,18, 2004. 2004 Wiley-Liss, Inc. [source]


    Nanoelectronic Biosensing of Dynamic Cellular Activities Based on Nanostructured Materials

    ADVANCED MATERIALS, Issue 25 2010
    Yinxi Huang
    Abstract Detecting subtle cellular activities that occur dynamically as regulated temporally and spatially by molecular machinery is of obvious importance in fundamental biology as well as in drug discovery. Additionally, it demands fast and sensitive detection modality. The emerging nanoelectronic biosensors based on nanostructured materials have shown promising potential to resolve the dynamic biological processes of living cells with high sensitivity and high temporal and spatial resolution. Here, the recent advances in the nanoelectronic biosensing of regulated secretion of biomolecules and bioelectrical activities of ion channels using carbon nanotubes and silicon nanowires are briefly reviewed. The perspectives and key issues of future development are also discussed. [source]


    Causes and consequences of fire-induced soil water repellency

    HYDROLOGICAL PROCESSES, Issue 15 2001
    J. Letey
    Abstract A wettable surface layer overlying a water-repellent layer is commonly observed following a fire on a watershed. High surface temperatures ,burn' off organic materials and create vapours that move downward in response to a temperature gradient and then condense on soil particles causing them to become water repellent. Water-repellent soils have a positive water entry pressure hp that must be exceeded or all the water will runoff. Water ponding depths ho that exceeds hp will cause infiltration, but the profile is not completely wetted. Infiltration rate and soil wetting increase as the value of ho/hp increases. The consequence is very high runoff, which also contributes to high erosion on fire-induced water-repellent soils during rain storms. Grass establishment is impaired by seeds being eroded and lack of soil water for seeds that do remain and germinate. Extrapolation of these general findings to catchment or watershed scales is difficult because of the very high temporal and spatial variabilities that occur in the field. Copyright 2001 John Wiley & Sons, Ltd. [source]


    A gridded hourly precipitation dataset for Switzerland using rain-gauge analysis and radar-based disaggregation

    INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 12 2010
    Marc West
    Abstract Rain gauges and weather radars both constitute important devices for operational precipitation monitoring. Gauges provide accurate yet spotty precipitation estimates, while radars offer high temporal and spatial resolution yet at a limited absolute accuracy. We propose a simple methodology to combine radar and daily rain-gauge data to build up a precipitation dataset with hourly resolution covering a climatological time period. The methodology starts from a daily precipitation analysis, derived from a dense rain-gauge network. A sequence of hourly radar analyses is then used to disaggregate the daily analyses. The disaggregation is applied such as to retain the daily precipitation totals of the rain-gauge analysis, in order to reduce the impact of quantitative radar biases. Hence, only the radar's advantage in terms of temporal resolution is exploited. In this article the disaggregation method is applied to derive a 15-year gridded precipitation dataset at hourly resolution for Switzerland at a spatial resolution of 2 km. Validation of this dataset indicates that errors in hourly intensity and frequency are lower than 25% on average over the Swiss Plateau. In Alpine valleys, however, errors are typically larger due to shielding effects of the radar and the corresponding underestimation of precipitation periods by the disaggregation. For the flatland areas of the Swiss Plateau, the new dataset offers an interesting quantitative description of high-frequency precipitation variations suitable for climatological analyses of heavy events, the evaluation of numerical weather forecasting models and the calibration/operation of hydrological runoff models. Copyright 2009 Royal Meteorological Society [source]


    A synoptic-scale climate analysis of anomalous snow water equivalent over the Northern Great Plains of the USA

    INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 8 2003
    Andrew Grundstein
    Abstract The Northern Great Plains is a region where variations in seasonal snow accumulation can have a dramatic affect on regional hydrology. In the past, one of the problems in studying snow hydrology has been obtaining information of sufficiently high temporal and spatial resolution on the water content of the snowpack. This project used a hybrid climatology of snow water equivalent (SWE) that incorporated both model and observed data. This climatology has a long time series (49 years) and a high spatial resolution (1 1) sufficient for use in a climatic analysis. The long and complete time series of SWE generated in this project allowed for a comprehensive analysis of the meteorological and climate forcing mechanisms that influence the amount of SWE. The five largest (high SWE) and five smallest SWE (low SWE) accumulations on 1 March were examined. High SWE years received greater snowfall and fewer accumulated melting degree days throughout the season. Large SWE accumulations at the end of the season, however, were not always associated with deep snowpacks early in the season. Also, all five high SWE years had above normal snowfall in February. Years with small or no SWE had below-average snowfall but greater than average accumulated melting degree days. A synoptic analysis examined both atmospheric circulation and air mass frequencies to assess impacts on ablation and snowfall. A distinct difference in the frequency of different air mass during high SWE versus low SWE years was evident. High SWE years were characterized by substantially greater intrusions of the coldest and driest air mass type (dry polar). Low SWE years, in contrast, had a greater frequency of more moderate air masses (dry moderate and moist moderate). In years with above average SWE, negative departures in November,December,January,February composite 700 hPa field were evident across the continental USA and indicate a greater frequency of troughing across the study area. Low SWE years were characterized by a ridging pattern that reduced the likelihood of precipitation and may have aided in the intrusion of more moderate air masses. Copyright 2003 Royal Meteorological Society [source]


    High temporal and spatial resolution 4D MRA using spiral data sampling and sliding window reconstruction

    MAGNETIC RESONANCE IN MEDICINE, Issue 1 2004
    He Zhu
    Abstract Contrast-enhanced magnetic resonance angiography (CE-MRA) requires high spatial resolution to demonstrate detailed vasculature and high temporal resolution to capture the contrast bolus. Sparse bright voxels in MRA permit substantial undersampling in MRI data acquisition, allowing simultaneous high temporal and spatial resolution. We developed a time-resolved 3D MRA technique using the efficient spiral sampling trajectory, and performed off-resonance corrections using inhomogeneity field maps. View sharing and sliding window reconstruction were utilized to generate high temporal resolution. High-resolution 3D angiograms were generated at 1,2 s per frame, with a 5,8 ml gadolinium dose, in patients with vascular disease. Magn Reson Med 52:14,18, 2004. 2004 Wiley-Liss, Inc. [source]


    Monitoring and verifying cloud forecasts originating from operational numerical models

    METEOROLOGICAL APPLICATIONS, Issue 3 2008
    Christoph Zingerle
    Abstract Weather satellites produce large amounts of observational data in real time. This information has high temporal and spatial resolution covering almost every region of the globe. The infrared (IR) window channels of operational meteorological satellites are sensitive to the clouds and to the underlying surface. Comparing the IR channel observations with synthetic satellite images is an effective way to evaluate the quality of cloud forecasts produced by numerical models. Assessment of potentially problematic features in the early stages of the forecast is essential in not only nowcasting and very short-range forecasting but also in a reliability check of a given numerical weather prediction model (NWP). A pre-operational real-time monitoring system is set up in the Finnish Meteorological Institute, using the observed and synthetic satellite images, and applying an entity-based verification method. Copyright 2008 Royal Meteorological Society [source]


    An automated tracking system to measure the dynamic properties of vesicles in living cells

    MICROSCOPY RESEARCH AND TECHNIQUE, Issue 2 2007
    Tien-Chuan Ku
    Abstract Recent technological improvements have made it possible to examine the dynamics of individual vesicles at a very high temporal and spatial resolution. Quantification of the dynamic properties of secretory vesicles is labor-intensive and therefore it is crucial to develop software to automate the process of analyzing vesicle dynamics. Dual-threshold and binary image conversion were applied to enhance images and define the areas of objects of interest that were to be tracked. The movements, changes in fluorescence intensity, and changes in the area of each tracked object were measured using a new software system named the Protein Tracking system (PTrack). Simulations revealed that the system accurately recognized tracked objects and measured their dynamic properties. Comparison of the results from tracking real time-lapsed images manually with those automatically obtained using PTrack revealed similar patterns for changes in fluorescence intensity and a high accuracy (<89%). According to tracking results, PTrack can distinguish different vesicular organelles that are similar in shape, based on their unique dynamic properties. In conclusion, the novel tracking system, PTrack, should facilitate automated quantification of the dynamic properties of vesicles that are important when classifying vesicular protein locations. Microsc. Res. Tech. 2007. 2006 Wiley-Liss, Inc. [source]


    An observing-system experiment with ground-based GPS zenith total delay data using HIRLAM 3D-Var in the absence of satellite data

    THE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 650 2010
    Reima Eresmaa
    Abstract Ground-based receiver networks of the Global Positioning System (GPS) provide observations of atmospheric water vapour with a high temporal and horizontal resolution. Variational data assimilation allows researchers to make use of zenith total delay (ZTD) observations, which comprise the atmospheric effects on microwave signal propagation. An observing-system experiment (OSE) is performed to demonstrate the impact of GPS ZTD observations on the output of the High Resolution Limited Area Model (HIRLAM). The GPS ZTD observations for the OSE are provided by the EUMETNET GPS Water Vapour Programme, and they are assimilated using three-dimensional variational data assimilation (3D-Var). The OSE covers a five-week period during the late summer of 2008. In parallel with GPS ZTD data assimilation in the regular mode, the impact of a static bias-correction algorithm for the GPS ZTD data is also assessed. Assimilation of GPS ZTD data, without bias correction of any kind, results in a systematic increase in the forecast water-vapour content, temperature and tropospheric relative topography. A slightly positive impact is shown in terms of decreased forecast-error standard deviation of lower and middle tropospheric humidity and lower tropospheric geopotential height. Moreover, verification of categorical forecasts of 12 h accumulated precipitation shows a positive impact. The application of the static bias-correction scheme is positively verified in the case of the mean forecast error of lower tropospheric humidity and when relatively high precipitation accumulations are considered. Copyright 2010 Royal Meteorological Society [source]


    IMAGING LUNG AERATION AND LUNG LIQUID CLEARANCE AT BIRTH USING PHASE CONTRAST X-RAY IMAGING

    CLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 1 2009
    Stuart B Hooper
    SUMMARY 1The transition to extra-uterine life at birth is critically dependent on airway liquid clearance to allow the entry of air and the onset of gaseous ventilation. We have used phase contrast X-ray imaging to identify factors that regulate lung aeration at birth in spontaneously breathing term and mechanically ventilated preterm rabbit pups. 2Phase contrast X-ray imaging exploits the difference in refractive index between air and water to enhance image contrast, enabling the smallest air-filled structures of the lung (alveoli; < 100 m) to be resolved. Using this technique, the lungs become visible as they aerate, allowing the air,liquid interface to be observed as it moves distally during lung aeration. 3Spontaneously breathing term rabbit pups rapidly aerate their lungs, with most fully recruiting their functional residual capacity (FRC) within the first few breaths. The increase in FRC occurs mainly during individual breaths, demonstrating that airway liquid clearance and lung aeration is closely associated with inspiration. We suggest that transpulmonary pressures generated by inspiration provide a hydrostatic pressure gradient for the movement of water out of the airways and into the surrounding lung tissue after birth. 4In mechanically ventilated preterm pups, lung aeration is closely associated with lung inflation and a positive end-expiratory pressure is required to generate and maintain FRC after birth. 5In summary, phase contrast X-ray imaging can image the air-filled lung with high temporal and spatial resolution and is ideal for identifying factors that regulate lung aeration at birth in both spontaneously breathing term and mechanically ventilated preterm neonates. [source]