Bibliografías temáticas / Stigmatic surfaces

Literatura académica sobre el tema "Stigmatic surfaces"

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Publicado: 1 de abril de 2023

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Artículos de revistas sobre el tema "Stigmatic surfaces"

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Carmo-Oliveira, Renata y Berta Lange de Morretes. "Stigmatic surface in the Vochysiaceae: reproductive and taxonomic implications". Acta Botanica Brasilica 23, n.º 3 (septiembre de 2009): 780–85. http://dx.doi.org/10.1590/s0102-33062009000300018.

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The Vochysiaceae are Neotropical trees and shrubs, common in the savanna areas in Central Brazil (Cerrados). The family has been traditionally divided into two tribes: Erismeae, with three genera, and Vochysieae, with five genera. We investigated the stigmatic surface of six Vochysiaceae species, belonging to four genera of Vochysieae: Vochysia, Salvertia, Callisthene and Qualea. Flowers and buds at different developmental stages were collected. Morphological features were observed on fresh material and stigmatic receptivity was inferred based on esterasic activity. Pistils were fixed and embedded in paraplast and sectioned on a rotary microtome; the sections were stained before histological analysis. Stigmas of open flowers were also observed by scanning electron microscopy. Stigmas of all species were wet and showed esterasic activity at pre-anthesis and anthesis stages. Stigmatic surface was continuous with transmitting tissue of glandular nature. Vochysia and Salvertia stigmatic surfaces were formed by multicelular uniseriate hairs, and species of the remaining genera showed papillate surface. The exudate over mature stigmas in all species flowed without rupture of stigmatic surface and pollen tubes grew down between hairs or papillae. Differences on the stigmatic surface agreed with a phylogenetic reconstruction that separated two clades and indicated that Vochysieae is not monophyletic. Stigmatic features could not be associated with pollination and breeding systems.
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Wetzstein, Hazel Y. y S. Edward Law. "Enhanced Visualization of the Fine Structure of the Stigmatic Surface of Citrus using Pre-fixation Washes". Journal of the American Society for Horticultural Science 137, n.º 5 (septiembre de 2012): 290–93. http://dx.doi.org/10.21273/jashs.137.5.290.

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Stigma characteristics and morphology can be useful in taxonomic and phylogenetic studies, indicate relationships in stigma function and receptivity, and be valuable in evaluating pollen–stigma interactions. Problematic is that in some taxa, copious stigmatic exudate can obscure the fine structural details of the stigmatic surface. Such is the case for Citrus, which has a wet stigma type on which abundant exudate inundates surface papillae. The components of stigmatic surface compounds are highly heterogeneous and include carbohydrates, proteins, lipids, glycoproteins, and phenolic compounds. This study evaluated the efficacy of several pre-fixation wash treatments on removing surface exudate to visualize the underlying stigmatic surface. Wash treatments included various buffer solutions, surfactants, dilute acids/bases, and solvents. Stigmas prepared using conventional fixation methods in glutaraldehyde had considerable accumulations of reticulate surface deposits with stigmatic cells obscured. Pre-fixation washes containing solvents such as methanol, chloroform, and ethanol left accumulations of incompletely removed exudate and crystalline deposits. Alkaline water washes produced a crust-like deposit on stigma surfaces. Buffer washes left residues of plaque-like deposits with perforated areas. In contrast, excellent removal of stigmatic exudate was obtained with a pre-fixation wash composed of 0.2 M Tris buffer, pH 7.2, containing 0.2% Triton X-100 surfactant and allowed clear imaging of the stigma and surface papillae morphology. A central sinus and radially arranged openings on the stigmatic surface were clearly visible and shown for the first time using scanning electron microscopy (SEM).
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Courtial, Johannes, Stephen Oxburgh y Tomáš Tyc. "Direct stigmatic imaging with curved surfaces". Journal of the Optical Society of America A 32, n.º 3 (25 de febrero de 2015): 478. http://dx.doi.org/10.1364/josaa.32.000478.

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Wetzstein, Hazel Y. y Darrell Sparks. "Stigma-Pollen Interactions in Pecan". Journal of the American Society for Horticultural Science 114, n.º 2 (marzo de 1989): 355–59. http://dx.doi.org/10.21273/jashs.114.2.355.

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Abstract Early pollen-stigma responses were observed microscopically in controlled pollinations of pecan [Carya illinoensis (Wangenh) C. Koch]. Receptive stigmatic surfaces have rounded, basally attached projecting papillae with an irregularly patterned, noncopious exudate. Polarly flattened pollen, characteristic of grains at anthesis, becomes rounded and hydrated by 1 hr after pollination. Pollen tube emergence is visible within 3 hr of pollination, and extensive pollen tube growth on the stigma is apparent after 8 to 12 hr. Tube growth generally occurs along the stigmatic surface and between adjacent cells. Stigmatic cells collapse after pollen hydration and germination, with collapse extensive 24 hr after pollination. By 48 hr after pollination, stigmatic cells are flattened, and pollen grains and emerged pollen tubes have contents discharged with a similar collapse.
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Cui, Zhouqi, Regan B. Huntley, Neil P. Schultes, Kaleem U. Kakar, Ching-Hong Yang y Quan Zeng. "Expression of the Type III Secretion System Genes in Epiphytic Erwinia amylovora Cells on Apple Stigmas Benefits Endophytic Infection at the Hypanthium". Molecular Plant-Microbe Interactions® 34, n.º 10 (octubre de 2021): 1119–27. http://dx.doi.org/10.1094/mpmi-06-21-0152-r.

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Erwinia amylovora causes fire blight on rosaceous plants. One of the major entry points of E. amylovora into hosts is flowers, where E. amylovora proliferates epiphytically on stigmatic and hypanthium surfaces and, subsequently, causes endophytic infection at the hypanthium. The type III secretion system (T3SS) is an important virulence factor in E. amylovora. Although the role of T3SS during endophytic infection is well characterized, its expression during epiphytic colonization and role in the subsequent infection is less understood. Here, we investigated T3SS gene expression in epiphytic E. amylovora on stigma and hypanthium of apple flowers under different relative humidities (RH). On stigma surfaces, T3SS was expressed in a high percentage of E. amylovora cells, and its expression promoted epiphytic growth. On hypanthium surfaces, however, T3SS was expressed in fewer E. amylovora cells than on the stigma, and displayed no correlation with epiphytic growth, even though T3SS expression is essential for infection. E. amylovora cells grown on stigmatic surfaces and then flushed down to the hypanthium displayed a higher level of T3SS expression than cells grown on the hypanthium surface alone. Furthermore, E. amylovora cells precultured on stigma had a higher potential to infect flowers than E. amylovora cells precultured in a T3SS-repressive medium. This suggests that T3SS induction during the stigmatic epiphytic colonization may be beneficial for subsequent infection. Finally, epiphytic expression of T3SS was influenced by RH. Higher percentage of stigmatic E. amylovora cells expressed T3SS under high RH than under low RH. [Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .
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6

Zietsman, P. C. "Reproductive biology of Stomatium bolusiae (Aizoaceae: Ruschioideae)". Bothalia 43, n.º 1 (13 de enero de 2013): 23–28. http://dx.doi.org/10.4102/abc.v43i1.83.

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Flowers of Stomatium bolusiae are self-incompatible. The species exhibits crepuscular and nocturnal anthesis, exploiting two different pollination mechanisms. The structure of the hermaphroditic flower appears not to favour cross-pollination. The stigmata are never exposed to pollinating agents, which gain access to the floral rewards by forcing their way between the anthers. Clogging of the stigmatic surfaces by self-pollen is common. Nocturnal anthesis, concomitant with the nocturnal release of attractants and the offering of rewards, indicates that this species is primarily phalaenophilous and secondarily melittophilous, exhibiting a bimodal pollination system.
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Silva-Lora, Alberto y Rafael Torres. "Explicit Cartesian oval as a superconic surface for stigmatic imaging optical systems with real or virtual source or image". Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 476, n.º 2235 (marzo de 2020): 20190894. http://dx.doi.org/10.1098/rspa.2019.0894.

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Cartesian ovals, also known as rigorously stigmatic surfaces, are the simplest optical systems capable of producing a perfect point image. Exist both implicit and explicit expressions to represent these surfaces, but they treat both refractive and reflective surfaces independently. Because of the complexity of explicit expressions, the ray-tracing techniques for these surfaces are implemented using third-party software. In this paper, we express Cartesian ovals as a degenerated superconic curve and get a new explicit formulation for Cartesian ovals capable of treating image formation using both object and image points, either real or virtual, and in this formulation can deal with both reflective and refractive rigorously stigmatic surfaces. Finally, using the resultant expressions and the vector Snell–Descartes Law, we propose a self-contained analytical ray-tracing technique for all these surfaces.
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PANDA, SAURIS y J. J. F. E. DE WILDE. "Diversity and taxonomic value of stigmatic surfaces in Begoniaceae: SEM analysis". Acta Botanica Neerlandica 44, n.º 2 (junio de 1995): 139–50. http://dx.doi.org/10.1111/j.1438-8677.1995.tb00776.x.

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Doskolovich, L. L., D. A. Bykov, G. I. Greisukh y Y. S. Strelkov. "Design of a stigmatic lens with minimal Fresnel losses". Computer Optics 45, n.º 3 (junio de 2021): 350–55. http://dx.doi.org/10.18287/2412-6179-co-813.

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A method for designing double aspheric lenses enabling minimal Fresnel losses in the class of stigmatic lenses is considered. Minimization of the Fresnel losses is provided by ensuring equal ray-deviation angles on both aspheric surfaces of the lens. The design of the lens is reduced to the integration of an explicit ordinary differential equation. Simple analytical approximations for the lens profiles are also presented.
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10

Wood, Bruce W. "Flavonoids, Alkali Earth, and Rare Earth Elements Affect Pecan Pollen Germination". HortScience 52, n.º 1 (enero de 2017): 85–88. http://dx.doi.org/10.21273/hortsci11426-16.

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The factors regulating pecan [Carya illinoinensis (Wangenh.) K. Koch] pollen grain germination are poorly understood for both in vitro pollen viability tests and on receptive stigmatic surfaces of pistillate flowers. Potential regulating factors include flavonols, calcium (Ca), Ca-like alkali earth elements (AEEs), and rare earth elements (REEs). When various concentrations of certain naturally occurring simple flavonols (e.g., quercetin, kaempferol, myricetin, naringenin, and hesperetin) were tested in vitro by adding to standard pecan pollen germination medium, hesperetin, myricetin, and kaempferol functioned as a strong agonist at low concentration (0.12–2.0 µm for hesperetin and kaempferol, and 0.25 µm for myricetin), increasing pollen germination 2- to 3.9-fold over flavonol-free media. Hesperetin and myricetin were antagonistic at 16 µm. Kaempferol was not antagonistic at any concentration up to and including 16 µm. Naringenin was an antagonist at concentrations from 0.12 to 16 µm; whereas, quercetin was an antagonist at 8–16 µm, but tended to function as an agonist at low concentration (0.12–0.50 µm). The equal molar replacement of Ca2+ in standard pecan pollen germination media by single REEs, resulted in certain REEs [e.g., yttrium (Y), gadolinium (Gd), and thulium (Tm)] partially replacing the obligate need for Ca2+; thus, functioning as agonists in absence of Ca. All non-Ca AEEs [beryllium (Be), magnesium (Mg), strontium (Sr), expect for barium (Ba)], also partially substituted for Ca2+ at equivalent molar concentrations, but none were as efficacious as Ca2+. Results are suggestive that a) pollen germination in in vitro test can be improved by incorporation of certain flavonols, and b) pollen germination on stigmatic surfaces of flowers in orchards might be influenced or regulated by flavonol composition and Ca-like metals in the liquid matrix of the wet (receptive) stigmatic surface.
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Tesis sobre el tema "Stigmatic surfaces"

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KLEMAN, DREW T. "PSYCHOTIC/SEMANTIC: OF SIGNS, STIGMATA, AND THE HISTORICAL ASYLUM". University of Cincinnati / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1147909874.

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Capítulos de libros sobre el tema "Stigmatic surfaces"

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González-Acuña, Rafael G. y Héctor A. Chaparro-Romo. "Stigmatism and stigmatic reflective surfaces". En Stigmatic Optics. IOP Publishing, 2020. http://dx.doi.org/10.1088/978-0-7503-3463-1ch5.

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González-Acuña, Rafael G. y Héctor A. Chaparro-Romo. "Stigmatic refractive surfaces: the Cartesian ovals". En Stigmatic Optics. IOP Publishing, 2020. http://dx.doi.org/10.1088/978-0-7503-3463-1ch6.

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González-Acuña, Rafael G. y Héctor A. Chaparro-Romo. "General dioptric stigmatic surfaces". En Optical Path Theory. IOP Publishing, 2022. http://dx.doi.org/10.1088/978-0-7503-4705-1ch3.

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González-Acuña, Rafael G. y Héctor A. Chaparro-Romo. "General catoptric stigmatic surfaces". En Optical Path Theory. IOP Publishing, 2022. http://dx.doi.org/10.1088/978-0-7503-4705-1ch2.

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González-Acuña, Rafael G. y Héctor A. Chaparro-Romo. "General freeform dioptric stigmatic surfaces". En Optical Path Theory. IOP Publishing, 2022. http://dx.doi.org/10.1088/978-0-7503-4705-1ch7.

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Actas de conferencias sobre el tema "Stigmatic surfaces"

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Braat, Joseph. "Design of an optical system towards some isoplanatic prescription". En International Optical Design Conference. Washington, D.C.: Optica Publishing Group, 1998. http://dx.doi.org/10.1364/iodc.1998.lmb.1.

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When designing an imaging optical system with an extended imaging region or volume, either an appreciable number of refracting or reflecting surfaces is needed or a limited number of aspherical surfaces. The introduction of a single aspherical surface is sufficient to assure axial stigmatism. Interesting examples of the attainment of axial stigmatism with a single asphere are found in the class of surfaces of revolution which show a conical section when the surface is cut through the optical axis; the most well-known example is the paraboloid generating a perfect image of an infinitely distant object in its focus. In general, stigmatic imaging can be obtained by aspherizing one reflecting or refracting surface in an optical system [1]; other ’correcting’ means like a diffractive surface (DOE) or an inhomogeneous medium may equally serve to obtain the stigmatic imaging.
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2

Chastang, Jean-Claude. "Anticaustics". En OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1988. http://dx.doi.org/10.1364/oam.1988.tuf3.

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An anticaustic is the zero optical path wavefront corresponding to a given refracting or reflecting surface and a point source. The term anticaustic was coined by Jakob I Bernoulli in the 1690s. Anticaustics were introduced as they were easier to deal with mathematically than caustics. Anticaustics represent a curious case of interesting and possibly useful knowledge that fell into oblivion only to be resurrected much later but not without misconceptions. The anticaustics associated with the useful surfaces when the point sources are at finite distances are Descartes ovals or degeneracies thereof. The algebraic derivation of this fact is given. While mentioned briefly in textbooks in the context of stigmatic images, Descartes ovals are rapidly dismissed as being no more than curiosities. Yet they have many interesting properties. They are rarely represented correctly, i.e., as two nested closed loops, and the fact (known to Descartes) that a given oval has three foci, not two, is never mentioned. These properties and their optical consequences are reviewed. It should be noted that this is an example of wavefront tracing although very limited since only one surface is involved.
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Sigler, R. D. "Design, Fabrication, and Testing of an f/0.3 Achromatic Focusing System". En Optical Fabrication and Testing. Washington, D.C.: Optica Publishing Group, 1990. http://dx.doi.org/10.1364/oft.1980.ffb4.

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One of the crucial problems in laser fusion research is the efficient delivery of enormous amounts of power (typically several terawatts) to irradiate pellets of approximately 100 micrometer diameter. An illumination system consisting of a pair of ellipsoidal mirrors and aspheric single element lenses has been used with a two beam laser for several years at KMSF and has been very successful. 1. The lens surfaces are so steep that it is very difficult to apply anti-reflective coatings. 2. The lens must be very thick to accomodate short radii of curvature. The deleterious effects of high power beams propagating through refractive media are well known. 3. The lens also causes the system to be stigmatic for only one wavelength. The last item is especially important as recent experience has indicated that pellet energy absorption is increased by harmonically generated short wavelength and/or broadband laser light.
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