scholarly journals Peer Review #2 of "An adaptive scale Gaussian filter to explain White’s illusion from the viewpoint of lightness assimilation for a large range of variation in spatial frequency of the grating and aspect ratio of the targets (v0.2)"

2018 ◽  
Keyword(s):  
Aspect Ratio ◽  
Spatial Frequency ◽  
Peer Review ◽  
Large Range ◽  
Gaussian Filter ◽  
Range Of Variation

Belowground morphology and population dynamics of two forest understory herbs of contrasting growth form

Botany ◽  
2021 ◽  
Author(s):  
Joseph A. Antos ◽  
Donald B. Zobel ◽  
Dylan Fischer
Keyword(s):  
Pacific Northwest ◽  
Large Range ◽  
Forest Understory ◽  
Old Growth Forest ◽  
Forest Herbs ◽  
Understory Herbs ◽  
Small Roots ◽  
Chimaphila Umbellata ◽  
Range Of Variation ◽  
Xerophyllum Tenax

Forest understory herbs exhibit a large range of variation in morphology and life history. Here we expand the reported range of variation by describing the belowground structures of two very different species, Xerophyllum tenax and Chimaphila umbellata. We excavated individuals in forests of the Cascade Mountains, Pacific Northwest, USA. Xerophyllum tenax has short rhizomes, but an extensive root system that is exceptionally large among forest understory species. The roots reach 4 m in length and may occupy an area 50 times that of the aboveground canopy. In contrast, Chimaphila umbellata has very small roots, but an extensive rhizome system. The largest plant we excavated had 57 m of connected rhizomes and still had a seedling source. Both species have long-lived individuals but differ in response to disturbance. Based on monitoring of 151 permanent 1 m2 plots in an old-growth forest, X. tenax increased only minimally in density over 40 years following tephra deposition from the 1980 eruption of Mount St. Helens, whereas density of C. umbellata increased substantially. The very different morphology of these two species highlights the large range of variation found among forest herbs, which needs to be considered when examining the forest understory.

Stress Intensity Factors for Semi-Elliptical Surface Cracks With Flaw Aspect Ratio Beyond the ASME XI Limit

2009 ◽  
Author(s):  
Christian Malekian ◽  
Eric Wyart ◽  
Michael Savelsberg ◽  
Anne Teughels ◽  
Pierre-Eric Fouquet ◽  
...  
Keyword(s):  
Stress Intensity ◽  
Finite Elements ◽  
Aspect Ratio ◽  
Stress Intensity Factors ◽  
Large Range ◽  
Crack Depth ◽  
Surface Cracks ◽  
Intensity Factors ◽  
Flat Plates ◽  
Circular Shape

Most of the literature about fracture mechanics considers cracks having an elliptical shape with a flaw aspect ratio a/l lower or equal to 0.5 where ‘a’ is the crack depth and ‘l’ the total length of the crack. This is also case in the ASME XI Appendix A where Stress Intensity Factors KI formulations are given for a large range of crack depths and for a flaw aspect ratio a/l between 0 and 0.5. The limitation to 0.5 corresponds to a semi-circular shape for surface cracks and to a circular shape for subsurface cracks. This limitation does not seem to be inspired by a theoretical limitation nor by a computational limit. Moreover, it appears that limiting the ratio a/l to 0.5 may generate in some cases some unnecessary conservatism in flaw analysis. The present article specifically deals with the more unusual narrow cracks having a/l >0.5, in the case of surface cracks in infinite flat plates. Several Finite-Elements calculations are performed to compute KI for a large range of crack depths and for 4 typical load cases (uniform, linear, quadratic and cubic). The results can be presented with the same formalism as in the ASME XI Appendix A, such that the work can provide an extension of the ASME coefficients in table A-3320-1&2. By doing the study, one had the opportunity to compare the results obtained by two different Finite-Elements softwares (Systus and Ansys), each one with a different cracked mesh. In addition, a comparison has been made for some cases with results obtained by a XFEM approach (eXtended Finite-Element Method), where the crack does not need to be meshed in the same way as in classical Finite-Elements. The results indicate how the KI can be reduced when considering the real flaw aspect ratio instead of the conventional semi-circular flaw shape. They also show that, for specific theoretical stress distributions, it is not always possible to reduce the analysis of KI to only 2 points, namely the crack surface point and the crack deepest point. The crack growth evaluation of such unusual crack shape should still be investigated to verify whether simple rules can be established to estimate the evolution of the crack front.

Comparing the Spatial-Frequency Response of First-Order and Second-Order Lateral Visual Interactions: Grating Induction and Contrast – Contrast

Perception ◽  
10.1068/p5348 ◽  
2005 ◽  
Vol 34 (4) ◽  
pp. 501-510 ◽  
Author(s):  
Mark E McCourt
Keyword(s):  
Spatial Frequency ◽  
Large Range ◽  
Spatial Interaction ◽  
Significant Negative Correlation ◽  
Second Order ◽  
First Order ◽  
Low Pass ◽  
Common Unit ◽  
Visual Interactions ◽  
Contrast Matching

The magnitudes of two suprathreshold lateral spatial-interaction effects—grating induction and contrast–contrast—were compared with regard to their dependence upon inducing-grating spatial frequency. Both effects cause the contrast of target stimuli embedded in surrounding patterns to be matched nonveridically. The magnitudes of each effect were measured in a common unit that indexed the degree of nonveridical contrast matching across a large range of target-grating contrasts (±0.80). Grating induction was a low-pass effect with respect to spatial frequency, whereas contrast–contrast was bandpass, peaking at approximately 4.0 cycles deg−1. The magnitude of grating induction exceeded that of contrast – contrast, both overall and at their optimal frequencies (0.03125 and 4.0 cycles deg−1, respectively); the two effects are equipotent at an inducing-grating spatial frequency of 1.0 cycle deg−1. A significant negative correlation between the magnitudes of the two effects suggests a link whereby activation of second-order normalization mechanisms may inhibit first-order mechanisms.

scholarly journals Biofilm Formation of Clinical Klebsiella pneumoniae Strains Isolated from Tracheostomy Tubes and Their Association with Antimicrobial Resistance, Virulence and Genetic Diversity

Pathogens ◽  
2021 ◽  
Vol 10 (10) ◽  
pp. 1345
Author(s):  
Dorota Ochońska ◽  
Łukasz Ścibik ◽  
Monika Brzychczy-Włoch
Keyword(s):  
Genetic Diversity ◽  
Bacterial Adhesion ◽  
Biofilm Formation ◽  
Large Range ◽  
Bacterial Colonization ◽  
Genes Encoding ◽  
Invasive Infections ◽  
Tracheostomy Tubes ◽  
Range Of Variation

(1) Background: Due to the commonness of tracheotomy procedures and the wide use of biomaterials in the form of tracheostomy tubes (TTs), the problem of biomaterial-associated infections (BAIs) is growing. Bacterial colonization of TTs results in the development of biofilms on the surface of biomaterials, which may contribute to the development of invasive infections in tracheostomized patients. (2) Methods: Clinical strains of K. pneumoniae, isolated from TTs, were characterized according to their ability to form biofilms, as well as their resistance to antibiotics, whether they harbored ESβL genes, the presence of selected virulence factors and genetic diversity. (3) Results: From 53 patients, K. pneumoniae were detected in 18 of the TTs examined, which constitued 34% of all analyzed biomaterials. Three of the strains (11%) were ESβL producers and all had genes encoding CTX-M-1, SHV and TEM enzymes. 44.4% of isolates were biofilm formers, SEM demonstrating that K. pneumoniae formed differential biofilms on the surface of polyethylene (PE) and polyvinyl chloride (PVC) TTs in vitro. A large range of variation in the share of fimbrial genes was observed. PFGE revealed sixteen genetically distinct profiles. (4) Conclusions: Proven susceptibility of TT biomaterials to colonization by K. pneumoniae means that the attention of research groups should be focused on achieving a better understanding of the bacterial pathogens that form biofilms on the surfaces of TTs. In addition, research efforts should be directed at the development of new biomaterials or the modification of existing materials, in order to prevent bacterial adhesion to their surfaces.

scholarly journals The Island Name Krk, Croatia, in its Mediterranean and European Context

2020 ◽  
Vol 17 (3) ◽  
pp. 186-208
Author(s):  
Richard Coates ◽  
Keyword(s):  
Large Range ◽  
Pure Water ◽  
Doctoral Dissertation ◽  
Original Formulation ◽  
Cultural Significance ◽  
Ancient Greek ◽  
European Context ◽  
Geological Features ◽  
The Mediterranean ◽  
Range Of Variation

Krk is one of the two largest islands in the Adriatic archipelago of Croatia, along with Cres. Its name has been discussed most recently by Dubravka Ivšić Majić (Voprosy Onomastiki 16.1, 2019) in the context of an analysis of the survival of the pre-Slavic names of islands presently in Croatia that are recorded in medieval sources, which is based in part on her doctoral dissertation. However, Krk has apparently never been discussed in the wider perspective that is attempted here. The purposes of this article are (1) to examine a moderately large range of similar names in or adjacent to the Mediterranean (understood broadly to include the Ægean, Adriatic and Tyrrhenian Seas), and (2) to try to form a view about the possible origin and significance of the name and its etymon, along with their possible relation to certain other names and lexical words in languages of the Mediterranean, notably Ancient Greek, and Insular Celtic. Particular attention is paid to the geology, geomorphology and cultural significances of the places bearing names of this type. It is tentatively concluded that the names originally referred to striking geological features invested with cultural significance because of some exceptional additional characteristic, such as the mysterious appearance or disappearance of pure water. Certainty is not possible about the language of original formulation, but the range of variation in the nametypes and their apparent dialectology are considered. Greek is the medium of transmission for the majority of the names analysed. A brief footnote glance is taken at superficially comparable names and lexical items even further from the epicentre of the phenomena considered here.

scholarly journals An adaptive scale Gaussian filter to explain White’s illusion from the viewpoint of lightness assimilation for a large range of variation in spatial frequency of the grating and aspect ratio of the targets

PeerJ ◽  
2018 ◽  
Vol 6 ◽  
pp. e5626 ◽  
Author(s):  
Soma Mitra ◽  
Debasis Mazumdar ◽  
Kuntal Ghosh ◽  
Kamales Bhaumik
Keyword(s):  
Spatial Frequency ◽  
Gaussian Kernel ◽  
Linear Filter ◽  
Filter Model ◽  
Visual Neuroscience ◽  
Difference Of Gaussians ◽  
Simultaneous Brightness Contrast ◽  
Frequency Components ◽  
Lightness Induction ◽  
Range Of Variation

The variation between the actual and perceived lightness of a stimulus has strong dependency on its background, a phenomena commonly known as lightness induction in the literature of visual neuroscience and psychology. For instance, a gray patch may perceptually appear to be darker in a background while it looks brighter when the background is reversed. In the literature it is further reported that such variation can take place in two possible ways. In case of stimulus like the Simultaneous Brightness Contrast (SBC), the apparent lightness changes in the direction opposite to that of the background lightness, a phenomenon often referred to as lightness contrast, while in the others like neon colour spreading or checkerboard illusion it occurs opposite to that, and known as lightness assimilation. The White’s illusion is a typical one which according to many, does not completely conform to any of these two processes. This paper presents the result of quantification of the perceptual strength of the White’s illusion as a function of the width of the background square grating as well as the length of the gray patch. A linear filter model is further proposed to simulate the possible neurophysiological phenomena responsible for this particular visual experience. The model assumes that for the White’s illusion, where the edges are strong and quite a few, i.e., the spectrum is rich in high frequency components, the inhibitory surround in the classical Difference-of-Gaussians (DoG) filter gets suppressed, and the filter essentially reduces to an adaptive scale Gaussian kernel that brings about lightness assimilation. The linear filter model with a Gaussian kernel is used to simulate the White’s illusion phenomena with wide variation of spatial frequency of the background grating as well as the length of the gray patch. The appropriateness of the model is presented through simulation results, which are highly tuned to the present as well as earlier psychometric results.

Sign in / Sign up

Export Citation Format

Share Document