283 research outputs found

    Zones of information in the AVIRIS spectra

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    To make the best use of Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) data an investigator needs to know the ratio of signal to random variability or noise (S/N ratio). The signal is land-cover dependent and decreases with both wavelength and atmospheric absorption and random noise comprises sensor noise and intra-pixel variability. The three existing methods for estimating the S/N ratio are inadequate as typical laboratory methods inflate, while dark current and image methods deflate the S/N ratio. We propose a new procedure called the geostatistical method. It is based on the removal of periodic noise by notch filtering in the frequency domain and the isolation of sensor noise and intra-pixel variability using the semi-variogram. This procedure was applied easily and successfully to five sets of AVIRIS data from the 1987 flying season

    Estimating the signal-to-noise ratio of AVIRIS data

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    To make the best use of narrowband airborne visible/infrared imaging spectrometer (AVIRIS) data, an investigator needs to know the ratio of signal to random variability or noise (signal-to-noise ratio or SNR). The signal is land cover dependent and varies with both wavelength and atmospheric absorption; random noise comprises sensor noise and intrapixel variability (i.e., variability within a pixel). The three existing methods for estimating the SNR are inadequate, since typical laboratory methods inflate while dark current and image methods deflate the SNR. A new procedure is proposed called the geostatistical method. It is based on the removal of periodic noise by notch filtering in the frequency domain and the isolation of sensor noise and intrapixel variability using the semi-variogram. This procedure was applied easily and successfully to five sets of AVIRIS data from the 1987 flying season and could be applied to remotely sensed data from broadband sensors

    Seasonal LAI in slash pine estimated with LANDSAT TM

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    The leaf area index (LAI, total area of leaves per unit area of ground) of most forest canopies varies throughout the year, yet for logistical reasons it is difficult to estimate anything more detailed than a seasonal maximum LAI. To determine if remotely sensed data can be used to estimate LAI seasonally, field measurements of LAI were compared to normalized difference vegetation index (NDVI) values derived using LANDSAT Thematic Mapper (TM) data, for 16 fertilized and control slash pine plots on 3 dates. Linear relationships existed between NDVI and LAI with R(sup 2) values of 0.35, 0.75, and 0.86 for February 1988, September 1988, and March, 1989, respectively. This is the first reported study in which NDVI is related to forest LAI recorded during the month of sensor overpass. Predictive relationships based on data from eight of the plots were used to estimate the LAI of the other eight plots with a root-mean-square error of 0.74 LAI, which is 15.6 percent of the mean LAI. This demonstrates the potential use of LANDSAT TM data for studying seasonal dynamics in forest canopies

    Linking teachers' memory-relevant language and the development of children's memory skills.

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    This longitudinal study was designed to (i) examine changes in childrenā€™s deliberate memory across the first grade; (ii) characterize the memory-relevant aspects of their classrooms; and (iii) explore linkages between the childrenā€™s performance and the language their teachers use in instruction. In order to explore contextual factors that may facilitate the development of skills for remembering, 107 first graders were assessed three times with a broad set of tasks, while extensive observations were made in the 14 classrooms from which these children were sampled. When the participating teachers were classified as high or low in terms of their ā€œmnemonic orientation,ā€ in part on the basis of their use of metacognitive information and requests for deliberate remembering during instruction in language arts and mathematics, differences were observed in the use of mnemonic techniques by the children in their classes. By the end of the year, the children drawn from these two groups of classrooms differed in their spontaneous use of simple behavioral strategies for remembering and in their response to training in more complex verbally-based mnemonic techniques

    A Survey Study of Resuscitation Skills Retention Amongst Health Providers in Newfoundland and Labrador: Final Report of Study Findings

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    The purpose of this report is to summarize the findings of a research study conducted between July 2010 and June 2011. The objectives of this study were threefold: 1. To examine the perceptions and attitudes of certified resuscitation providers towards the retention of resuscitation skills and regular skills updating. 2. To examine resuscitation providersā€™ self-efficacy beliefs towards resuscitation skills. 3. To explore resuscitation providerā€™s perceptions of methods and modalities for enhancing resuscitation skills retention

    Targeted deletion of a 170-kb cluster of LINE-1 repeats and implications for regional control.

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    Approximately half the mammalian genome is composed of repetitive sequences, and accumulating evidence suggests that some may have an impact on genome function. Here, we characterized a large array class of repeats of long-interspersed elements (LINE-1). Although widely distributed in mammals, locations of such arrays are species specific. Using targeted deletion, we asked whether a 170-kb LINE-1 array located at a mouse imprinted domain might function as a modulator of local transcriptional control. The LINE-1 array is lamina associated in differentiated ES cells consistent with its AT-richness, and although imprinting occurs both proximally and distally to the array, active LINE-1 transcripts within the tract are biallelically expressed. Upon deletion of the array, no perturbation of imprinting was observed, and abnormal phenotypes were not detected in maternal or paternal heterozygous or homozygous mutant mice. The array does not shield nonimprinted genes in the vicinity from local imprinting control. Reduced neural expression of protein-coding genes observed upon paternal transmission of the deletion is likely due to the removal of a brain-specific enhancer embedded within the LINE array. Our findings suggest that presence of a 170-kb LINE-1 array reflects the tolerance of the site for repeat insertion rather than an important genomic function in normal development

    Activating Fc Ī³ receptors contribute to the antitumor activities of immunoregulatory receptor-targeting antibodies

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    Fc Ī³ receptor (FcĪ³R) coengagement can facilitate antibody-mediated receptor activation in target cells. In particular, agonistic antibodies that target tumor necrosis factor receptor (TNFR) family members have shown dependence on expression of the inhibitory FcĪ³R, FcĪ³RIIB. It remains unclear if engagement of FcĪ³RIIB also extends to the activities of antibodies targeting immunoregulatory TNFRs expressed by T cells. We have explored the requirement for activating and inhibitory FcĪ³Rs for the antitumor effects of antibodies targeting the TNFR glucocorticoid-induced TNFR-related protein (GITR; TNFRSF18; CD357) expressed on activated and regulatory T cells (T reg cells). We found that although FcĪ³RIIB was dispensable for the in vivo efficacy of anti-GITR antibodies, in contrast, activating FcĪ³Rs were essential. Surprisingly, the dependence on activating FcĪ³Rs extended to an antibody targeting the non-TNFR receptor CTLA-4 (CD152) that acts as a negative regulator of T cell immunity. We define a common mechanism that correlated with tumor efficacy, whereby antibodies that coengaged activating FcĪ³Rs expressed by tumor-associated leukocytes facilitated the selective elimination of intratumoral T cell populations, particularly T reg cells. These findings may have broad implications for antibody engineering efforts aimed at enhancing the therapeutic activity of immunomodulatory antibodies
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