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Frequency Histograms (frequency + histogram)

Distribution by Scientific Domains

Life Sciences	50%

Selected Abstracts

A method of new filter design based on the co-occurrence histogram

ELECTRICAL ENGINEERING IN JAPAN, Issue 1 2009
Takayuki Fujiwara
Abstract We have proposed that the co-occurrence frequency image (CFI) based on the co-occurrence frequency histogram of the gray value of an image can be used in a new scheme for image feature extraction. This paper proposes new enhancement filters to achieve sharpening and smoothing of images. These filters are very similar in result but quite different in process from those which have been used previously. Thus, we show the possibility of a new paradigm for basic image enhancement filters making use of the CFI. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 166(1): 36,42, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20699 [source]

Recruitment patterns of six species of cyprinid fishes in the lower River Trent, England

ECOLOGY OF FRESHWATER FISH, Issue 2 2002
A. D. Nunn
Abstract,,,Fisheries data were collected for six species of 0-group cyprinid fishes from eight sites in the lower reaches of the River Trent, England, between May and October 1999 inclusive, using a micromesh seine net. Recruitment and growth patterns were observed via monthly length,frequency histograms and estimations of mean length. In the cases of roach and dace, growth was approximately linear through the summer, before declining in September and October. In the cases of chub and gudgeon, and to a lesser extent bream and bleak, however, there were suggestions of multiple recruitment events. It is argued that some of the fish species examined in the present study adopt fractional or protracted spawning strategies in the lower River Trent. [source]

Interval type-2 fuzzy logic for edges detection in digital images

INTERNATIONAL JOURNAL OF INTELLIGENT SYSTEMS, Issue 11 2009
Olivia Mendoza
Edges detection in a digital image is the first step in an image recognition system. In this paper, we show an efficient edges detector using an interval type-2 fuzzy inference system (FIS-2). The FIS-2 uses as input the original images after applying Sobel filters and attenuation filters, then the fuzzy rules infer normalized values for the edges images, especially useful to enhance the performance of neural networks. To illustrate the results, we built frequency histograms of some images and compare the results of the FIS-2 edge's detector with the gradient magnitude method and a type-1 fuzzy inference system (FIS-1). The FIS-2 results are better than the gradient magnitude and FIS-1, because the edges preserve more detail of the original images, and the backgrounds are more homogeneous than with FIS-1 and the gradient's magnitude method. © 2009 Wiley Periodicals, Inc. [source]

Use of Cell-Specific PAM-Fluorometry to Characterize Host Shading in the Epiphytic Dinoflagellate Gambierdiscus toxicus

MARINE ECOLOGY, Issue 2 2002
Tracy A. Villareal
Abstract. Cell-specific fluorescence characteristics were used to characterize the light tolerance of the toxic benthic dinoflagellate Gambierdiscus toxicus. The fluorescence parameter Fv : Fm was measured using pulse amplitude modulation (PAM) fluorometry on individual cells collected from foliose red algae growing in the sub-tidal margin of South Water Cay, Belize. Samples were collected over several days during sunny and cloudy conditions and compared to samples incubated in situ. The data from individual cells were used to generate both Fv : Fm frequency histograms and averages. Maximum individual cell values of Fv : Fm reached 0.81 in pre-dawn samples, a value near the theoretical maximum for PAM fluorometry. In field samples from macroalgal hosts, average Fv : Fm values declined only slightly during the day, but cells incubated in bottles under 47 % incident sunlight showed a significant mid-day depression. In freshly collected samples, near-maximum Fv : Fm values could be found in individual cells during the entire day; however, the frequency histograms indicated a greater range in Fv : Fm values during the afternoon than in the morning. In contrast, cultures of G. toxicus showed a tight distribution around a mean. Field samples showed a rapid recovery to near-maximum Fv : Fm within 2 min when assayed using a standardized actinic light series. Similar results were obtained in laboratory cultures of G. toxicus grown at 73 µmol photons · m -2 · s -1, but not at 383 µmol photons · m -2 · s -1. These data provide empirical support for suggestions that G. toxicus exploits the three-dimensional structure of the algal host thallus to minimize light exposure. This strategy permits G. toxicus, a high-light intolerant species in culture, to thrive in shallow, well-lit tropical seas. It may also partially explain the observed preference of G. toxicus for complex, foliose macroalgae as hosts. [source]

Diffusion-weighted magnetic resonance imaging of white matter in bipolar disorder: a pilot study

BIPOLAR DISORDERS, Issue 2 2006
William T Regenold
Objective:, Diffusion-weighted magnetic resonance imaging (MRI) has shown increased sensitivity in detecting brain white matter disease compared to traditional T2-weighted MRI. Diffusion-weighted imaging (DWI) can quantitatively assess the microstructural integrity of white matter using the average apparent diffusion coefficient (ADCav), a measure of the extent to which water molecules move freely within tissue. On the basis of numerous studies suggesting white matter disease in bipolar patients, particularly patients with more severe illness, this study aimed to test the utility of DWI in assessing the white matter integrity of bipolar patients with severe illness. Methods:, The existing MRI scans of eight bipolar patients and eight age-matched controls with neurological illness were examined retrospectively. ADCav values for pixels within white matter regions of interest (ROIs) were calculated and used to plot ADCav frequency histograms for each ROI. Mean ADCav values for the two groups were then compared by ANCOVA. Results:, The bipolar mean ADCav (0.855 ± 0.051 × 10,3 mm2/s) for combined white matter ROIs significantly exceeded that of controls (0.799 ± 0.046 × 10,3 mm2/s), while covarying for age (F = 4.47, df = 3, p = 0.025). Conclusions:, This is the first report of an elevated ADCav in the white matter of a group of patients with bipolar disorder. In this group of patients with severe illness, increased white matter ADCav suggests microstructural changes consistent with decreased white matter integrity. DWI may be an additional, useful tool to assess white matter abnormalities in bipolar disorder. [source]