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Facial wrinkling in men and women, by smoking status.

Ernster, V L; Grady, D; Miike, R; Black, D; Selby, J; Kerlikowske, K
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /01/1995 EN
Relevância na Pesquisa
27.72%
OBJECTIVES. This study examined the association of smoking status and pack-years of smoking with facial wrinkling in men and women. METHODS. We conducted a cross-sectional study of 299 never smokers, 551 former smokers and 286 current smokers, aged 30 through 69 years, drawn from a health maintenance organization. Smoking status, pack-years of smoking, and potential confounding variables were assessed by questionnaire. Facial wrinkle category, a dichotomous variable, and facial wrinkle score, a computed continuous variable, were assessed by blinded standardized visual assessment. Wrinkling was so uncommon among 30- through 39-year-old subjects that analyses were restricted to subjects aged 40 and over (227 never smokers, 456 former smokers, and 228 current smokers). RESULTS. With age, average sun exposure, and body mass index controlled, the estimated relative risk of moderate/severe wrinkling for current smokers compared to never smokers was 2.3 (95% confidence interval [CI] = 1.2, 4.2) among men and 3.1 (95% CI = 1.6, 5.9) among women. Pack-years was positively associated with facial wrinkle score in women aged 40 through 69 years and in men aged 40 through 59 years. In both groups, the increased risk of wrinkling was equivalent to about 1.4 years of aging. CONCLUSIONS. Our results support earlier findings that risk of facial wrinkling is greater in cigarette smokers than in never smokers.

Prototypical model for tensional wrinkling in thin sheets

Davidovitch, Benny; Schroll, Robert D.; Vella, Dominic; Adda-Bedia, Mokhtar; Cerda, Enrique A.
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
27.51%
The buckling and wrinkling of thin films has recently seen a surge of interest among physicists, biologists, mathematicians, and engineers. This activity has been triggered by the growing interest in developing technologies at ever-decreasing scales and the resulting necessity to control the mechanics of tiny structures, as well as by the realization that morphogenetic processes, such as the tissue-shaping instabilities occurring in animal epithelia or plant leaves, often emerge from mechanical instabilities of cell sheets. Although the most basic buckling instability of uniaxially compressed plates was understood by Euler more than two centuries ago, recent experiments on nanometrically thin (ultrathin) films have shown significant deviations from predictions of standard buckling theory. Motivated by this puzzle, we introduce here a theoretical model that allows for a systematic analysis of wrinkling in sheets far from their instability threshold. We focus on the simplest extension of Euler buckling that exhibits wrinkles of finite length—a sheet under axisymmetric tensile loads. The first study of this geometry, which is attributed to Lamé, allows us to construct a phase diagram that demonstrates the dramatic variation of wrinkling patterns from near-threshold to far-from-threshold conditions. Theoretical arguments and comparison to experiments show that the thinner the sheet is...

Using Dental Enamel Wrinkling to Define Sauropod Tooth Morphotypes from the Cañadón Asfalto Formation, Patagonia, Argentina

Holwerda, Femke M.; Pol, Diego; Rauhut, Oliver W. M.
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 18/02/2015 EN
Relevância na Pesquisa
27.51%
The early Middle Jurassic is regarded as the period when sauropods diversified and became major components of the terrestrial ecosystems. Not many sites yield sauropod material of this time; however, both cranial and postcranial material of eusauropods have been found in the Cañadón Asfalto Formation (latest Early Jurassic–early Middle Jurassic) in Central Patagonia (Argentina), which may help to shed light on the early evolution of eusauropods. These eusauropod remains include teeth associated with cranial and mandibular material as well as isolated teeth found at different localities. In this study, an assemblage of sauropod teeth from the Cañadón Asfalto Formation found in four different localities in the area of Cerro Condor (Chubut, Argentina) is used as a mean of assessing sauropod species diversity at these sites. By using dental enamel wrinkling, primarily based on the shape and orientation of grooves and crests of this wrinkling, we define and describe three different morphotypes. With the exception of one taxon, for which no cranial material is currently known, these morphotypes match the local eusauropod diversity as assessed based on postcranial material. Morphotype I is tentatively assigned to Patagosaurus, whereas morphotypes II and III correspond to new taxa...

Biological Mechanisms Underlying the Ultraviolet Radiation-Induced Formation of Skin Wrinkling and Sagging I: Reduced Skin Elasticity, Highly Associated with Enhanced Dermal Elastase Activity, Triggers Wrinkling and Sagging

Imokawa, Genji; Ishida, Koichi
Fonte: MDPI Publicador: MDPI
Tipo: Artigo de Revista Científica
Publicado em 08/04/2015 EN
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27.63%
The repetitive exposure of skin to ultraviolet B (UVB) preferentially elicits wrinkling while ultraviolet A (UVA) predominantly elicits sagging. In chronically UVB or UVA-exposed rat skin there is a similar tortuous deformation of elastic fibers together with decreased skin elasticity, whose magnitudes are greater in UVB-exposed skin than in UVA-exposed skin. Comparison of skin elasticity with the activity of matrix metalloproteinases (MMPs) in the dermis of ovariectomized rats after UVB or UVA irradiation demonstrates that skin elasticity is more significantly decreased in ovariectomized rats than in sham-operated rats, which is accompanied by a reciprocal increase in elastase activity but not in the activities of collagenases I or IV. Clinical studies using animal skin and human facial skin demonstrated that topical treatment with a specific inhibitor or an inhibitory extract of skin fibroblast-derived elastase distinctly attenuates UVB and sunlight-induced formation of wrinkling. Our results strongly indicated that the upregulated activity of skin fibroblast-derived elastase plays a pivotal role in wrinkling and/or sagging of the skin via the impairment of elastic fiber configuration and the subsequent loss of skin elasticity.

Biological Mechanisms Underlying the Ultraviolet Radiation-Induced Formation of Skin Wrinkling and Sagging II: Over-Expression of Neprilysin Plays an Essential Role

Imokawa, Genji; Nakajima, Hiroaki; Ishida, Koichi
Fonte: MDPI Publicador: MDPI
Tipo: Artigo de Revista Científica
Publicado em 08/04/2015 EN
Relevância na Pesquisa
27.33%
Our previous studies strongly indicated that the up-regulated activity of skin fibroblast-derived elastase plays a pivotal role in wrinkling and/or sagging of the skin via the impairment of elastic fiber configuration and the subsequent loss of skin elasticity. Fortunately, we succeeded in identifying human skin fibroblast-derived elastase as a previously known enzyme, neprilysin or neutral endopeptidase (NEP). We have also characterized epithelial-mesenchymal paracrine cytokine interactions between UVB-exposed-keratinocytes and dermal fibroblasts and found that interleukin-1α and granulocyte macrophage colony stimulatory factor (GM-CSF) are intrinsic cytokines secreted by UVB-exposed keratinocytes that stimulate the expression of neprilysin by fibroblasts. On the other hand, direct UVA exposure of human fibroblasts significantly stimulates the secretion of IL-6 and also elicits a significant increase in the gene expression of matrix metallo-protease(MMP)-1 as well as neprilysin (to a lesser extent), which is followed by distinct increases in their protein and enzymatic activity levels. Direct UVA exposure of human keratinocytes also stimulates the secretion of IL-6, IL-8 and GM-CSF but not of IL-1 and endothelin-1. These findings suggest that GM-CSF secreted by UVA-exposed keratinocytes as well as IL-6 secreted by UVA-exposed dermal fibroblasts play important and additional roles in UVA-induced sagging and wrinkling by up-regulation of neprilysin and MMP-1...

Localized Ridge Wrinkling of Stiff Films on Compliant Substrates

Hutchinson, John W.; Cao, Yanping; Zang, Jianfeng; Zhao, Xuanhe
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
EN_US
Relevância na Pesquisa
37.63%
Wrinkling of thin stiff films on thick compliant elastomeric substrates subject to plane strain compression is considered for cases in which the substrate is pre-stretched prior to film attachment. Advanced wrinkling modes are investigated that evolve as the systems are compressed beyond the onset of the primary sinusoidal wrinkling mode. If the substrate pre-stretch is greater than about 40%, an advanced mode in the form of a series of well-spaced ridges separated by relatively flat film is observed in the simulations. Our experiments reveal a localization mode in the form of alternating packets of large and small amplitude wrinkles, but not ridges, while ridge formation has been observed in other recent experiments. Measurements of undulation amplitudes have been made for wrinkle fields of stiff films formed by oxidation of the surface of pre-stretched PDMS substrates. Simulations have been performed with a finite element model and an analytical film/substrate model. The formation of the ridge mode is a consequence of the altered nonlinearity of the substrate produced by the pre-stretch. The role of the tangential substrate stiffness in suppressing localization at the ridges is also highlighted. If there is no substrate pre-stretch...

From Wrinkles to Creases in Elastomers: The Instability and Imperfection-Sensitivity of Wrinkling

Cao, Yanping; Hutchinson, John W.
Fonte: The Royal Society Publicador: The Royal Society
Tipo: Artigo de Revista Científica
EN_US
Relevância na Pesquisa
37.83%
The stability of the wrinkling mode experienced by a compressed half-space of neo-Hookean material is investigated using analytical and numerical methods to study the post-bifurcation behaviour of periodic solutions. It is shown that wrinkling is highly unstable owing to the nonlinear interaction among the multiple modes associated with the critical compressive state. Concomitantly, wrinkling is sensitive to exceedingly small initial imperfections that significantly reduce the compressive strain at which the instability occurs. The study provides insight into the connection between wrinkling and an alternative surface mode, the finite amplitude crease or sulcus. The shape of the critical combination of wrinkling modes has the form of an incipient crease, and a tiny initial imperfection can trigger a wrinkling instability that collapses into a crease.; Engineering and Applied Sciences

Wrinkling Phenomena in Neo-Hookean Film/Substrate Bilayers

Cao, Yanping; Hutchinson, John W.
Fonte: American Society of Mechanical Engineers Publicador: American Society of Mechanical Engineers
Tipo: Artigo de Revista Científica
EN_US
Relevância na Pesquisa
37.63%
Wrinkling modes are determined for a two-layer system comprised of a neo-Hookean film bonded to an infinitely deep neo-Hookean substrate with the entire bilayer undergoing compression. The full range of the film/substrate modulus ratio is considered from the limit of a traction-free homogeneous substrate to very stiff films on compliant substrates. The role of substrate prestretch is considered wherein an unstretched film is bonded to a prestretched substrate with wrinkling arising as the stretch in the substrate is relaxed. An exact bifurcation analysis reveals the critical strain in the film at the onset of wrinkling. Numerical simulations carried out within a finite element framework uncover advanced post-bifurcation modes including period-doubling, folding and a newly identified mountain ridge mode.; Engineering and Applied Sciences

The Role of Nonlinear Substrate Elasticity in the Wrinkling of Thin Films

Hutchinson, John W.
Fonte: The Royal Society Publicador: The Royal Society
Tipo: Artigo de Revista Científica
EN_US
Relevância na Pesquisa
37.72%
The role of substrate nonlinearity on the stability of wrinkling of thin films bonded to compliant substrates is investigated within the initial post-bifurcation range when wrinkling first emerges. A fully nonlinear neo-Hookean bilayer composed of a thin film on a deep substrate is analyzed for a wide range of the film/substrate stiffness ratio, from films that are very stiff compared to the substrate to those only slightly stiffer. Substrate pre-stretch prior to film attachment is shown to have a significant effect on the nonlinearity relevant to wrinkling. Two dimensionless parameters are identified which control the stability and mode shape evolution of the bilayer: one specifying arbitrary uniform substrate pre-stretch and the other a stretch- modified modulus ratio. For systems with film stiffness greater than about five times that of the substrate the wrinkling bifurcation is stable, while for systems with smaller relative film stiffness bifurcation can be unstable, especially if substrate pre-stretch is not tensile.; Engineering and Applied Sciences

The role of substrate pre-stretch in post-wrinkling bifurcations

Auguste, Anesia; Jin, Lihua; Suo, Zhigang; Hayward, Ryan C.
Fonte: Royal Society of Chemistry (RSC) Publicador: Royal Society of Chemistry (RSC)
Tipo: Artigo de Revista Científica
EN_US
Relevância na Pesquisa
27.51%
When a stiff film on a soft substrate is compressed, the surface of the film forms wrinkles, with tunable wavelengths and amplitudes that enable a variety of applications. As the compressive strain increases, the film undergoes post-wrinkling bifurcations, leading to period doubling and eventually to formation of localized folds or ridges. Here we study the post-wrinkling bifurcations in films on pre-stretched substrates. Through a combination of experiments and simulations, we demonstrate that pre-stretched substrates not only show substantial shifts in the critical strain for the onset of post-wrinkling bifurcations, but also exhibit qualitatively different post-wrinkled states. In particular, we report on the stabilization of wrinkles in films on pre-tensioned substrates and the emergence of ‘chaotic’ morphologies in films on pre-compressed substrates.; Engineering and Applied Sciences

Wrinkling and sagging of viscous sheets

Teichman, Jeremy Alan, 1975-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 134 p.; 4662413 bytes; 4662221 bytes; application/pdf; application/pdf
ENG
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27.33%
This thesis explores the wrinkling and sagging behavior of thin viscous Newtonian sheets and filaments motivated by analogous scenarios in elasticity. These problems involve dynamic free boundaries and geometric nonlinearities but use simple physics. The first problem examined concerns an annular viscous sheet subjected to torsional shearing which consequently develops spiral wrinkles. Examination of the behavior of this system leads to a scaling of the Stokes equations for zero Reynolds number flow resulting in a reduced order mathematical model for the evolution of the sheet that includes the effects of gravity and surface tension. Linear stability analysis yields the most unstable modes for wrinkling of the sheet and their associated growth rates at onset which agree with experimental observations. In the limit of a narrow annular gap, the problem reduces to that of a sheared rectilinear sheet. Interestingly, this Couette problem shows instabilities even in the zero Reynolds number limit. The second problem examined concerns the sagging of a horizontal viscida (fluid filament) under the influence of gravity. Resistance of the viscida to bending controls the initial phase of deformation, while resistance to stretching begins to play a principal role in later stages. At very late times the process resembles droplet break-off from two thin filaments.; by Jeremy Alan Teichman.; Thesis (Ph. D.)--Massachusetts Institute of Technology...

Graphene wrinkling induced by monodisperse nanoparticles: facile control and quantification

Vejpravova, Jana; Pacakova, Barbara; Endres, Jan; Mantlikova, Alice; Verhagen, Tim; Vales, Vaclav; Frank, Otakar; Kalbac, Martin
Fonte: Nature Publishing Group Publicador: Nature Publishing Group
Tipo: Artigo de Revista Científica
Publicado em 04/11/2015 EN
Relevância na Pesquisa
27.33%
Controlled wrinkling of single-layer graphene (1-LG) at nanometer scale was achieved by introducing monodisperse nanoparticles (NPs), with size comparable to the strain coherence length, underneath the 1-LG. Typical fingerprint of the delaminated fraction is identified as substantial contribution to the principal Raman modes of the 1-LG (G and G’). Correlation analysis of the Raman shift of the G and G’ modes clearly resolved the 1-LG in contact and delaminated from the substrate, respectively. Intensity of Raman features of the delaminated 1-LG increases linearly with the amount of the wrinkles, as determined by advanced processing of atomic force microscopy data. Our study thus offers universal approach for both fine tuning and facile quantification of the graphene topography up to ~60% of wrinkling.

Surface Wrinkling on Polydimethylsiloxane Microspheres via Wet Surface Chemical Oxidation

Yin, Jian; Han, Xue; Cao, Yanping; Lu, Conghua
Fonte: Nature Publishing Group Publicador: Nature Publishing Group
Tipo: Artigo de Revista Científica
Publicado em 16/07/2014 EN
Relevância na Pesquisa
27.33%
Here we introduce a simple low-cost yet robust method to realize spontaneously wrinkled morphologies on spherical surfaces. It is based on surface chemical oxidation of aqueous-phase-synthesized polydimethylsiloxane (PDMS) microspheres in the mixed H2SO4/HNO3/H2O solution. Consequently, curvature and overstress-sensitive wrinkles including dimples and labyrinth patterns are successfully induced on the resulting oxidized PDMS microspheres. A power-law dependence of the wrinkling wavelength on the microsphere radius exists. The effects of experimental parameters on these tunable spherical wrinkles have been systematically investigated, when the microspheres are pre-deposited on a substrate. These parameters include the radius and modulus of microspheres, the mixed acid solution composition, the oxidation duration, and the water washing post-treatment. Meanwhile, the complicated chemical oxidation process has also been well studied by in-situ optical observation via the microsphere system, which represents an intractable issue in a planar system. Furthermore, we realize surface wrinkled topographies on the whole microspheres at a large scale, when microspheres are directly dispersed in the mixed acid solution for surface oxidation. These results indicate that the introduced wet surface chemical oxidation has the great potential to apply to other complicated curved surfaces for large-scale generation of well-defined wrinkling patterns...

Quantification of thickness and wrinkling of exfoliated two-dimensional zeolite nanosheets

Kumar, Prashant; Agrawal, Kumar Varoon; Tsapatsis, Michael; Mkhoyan, K. Andre
Fonte: Nature Pub. Group Publicador: Nature Pub. Group
Tipo: Artigo de Revista Científica
Publicado em 11/05/2015 EN
Relevância na Pesquisa
27.33%
Some two-dimensional (2D) exfoliated zeolites are single- or near single-unit cell thick silicates that can function as molecular sieves. Although they have already found uses as catalysts, adsorbents and membranes precise determination of their thickness and wrinkling is critical as these properties influence their functionality. Here we demonstrate a method to accurately determine the thickness and wrinkles of a 2D zeolite nanosheet by comprehensive 3D mapping of its reciprocal lattice. Since the intensity modulation of a diffraction spot on tilting is a fingerprint of the thickness, and changes in the spot shape are a measure of wrinkling, this mapping is achieved using a large-angle tilt-series of electron diffraction patterns. Application of the method to a 2D zeolite with MFI structure reveals that the exfoliated MFI nanosheet is 1.5 unit cells (3.0 nm) thick and wrinkled anisotropically with up to 0.8 nm average surface roughness.

Mechanical Self-Assembly of a Strain-Engineered Flexible Layer: Wrinkling, Rolling, and Twisting

Chen, Zi; Huang, Gaoshan; Trase, Ian; Han, Xiaomin; Mei, Yongfeng
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 09/12/2015
Relevância na Pesquisa
27.33%
Self-shaping of curved structures, especially those involving flexible thin layers, has attracted increasing attention because of their broad potential applications in e.g. nanoelectromechanical/micro-electromechanical systems (NEMS/MEMS), sensors, artificial skins, stretchable electronics, robotics, and drug delivery. Here, we provide an overview of recent experimental, theoretical, and computational studies on the mechanical self-assembly of strain-engineered thin layers, with an emphasis on systems in which the competition between bending and stretchingenergy gives rise to a variety ofdeformations,such as wrinkling, rolling, and twisting. We address the principle of mechanical instabilities, which is often manifested in wrinkling or multistability of strain-engineered thin layers. The principles of shape selection and transition in helical ribbons are also systematically examined. We hope that a more comprehensive understanding of the mechanical principles underlying these rich phenomena can foster the development of new techniques for manufacturing functional three- dimensional structures on demand for a broad spectrum of engineering applications.; Comment: 91 pages, 35 figures, review article

Modelling of the subgrid scale wrinkling factor for large-eddy simulation of turbulent premixed combustion

Thiesset, F.; Maurice, G.; Halter, F.; Mazellier, N.; Chauveau, C.; Gökalp, I.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 28/12/2014
Relevância na Pesquisa
27.51%
We propose a model for assessing the unresolved wrinkling factor in LES of turbulent premixed combustion. It relies essentially on a power-law dependence of the wrinkling factor to the filter size and an original expression for the active corrugating strain rate. The latter is written as a product of an efficiency function which accounts for viscous effects and the kinematic constraint of Peters, by a recent expression for the turbulent strain intensity. Yields functional expressions for the fractal dimension and the inner cut-off length scale, the latter being (i) filter-size independent and (ii) consistent with the Damk\"ohler asymptotic behaviors at both large and small Karlovitz numbers. A new expression for the wrinkling factor which incorporates finite Reynolds numbers effects is further proposed. Finally, the model is successfully assessed on an experimental filtered database.; Comment: In preparation, 6 pages, 2 figures

Wrinkling of Random and Regular Semiflexible Polymer Networks

Müller, Pascal; Kierfeld, Jan
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 05/06/2014
Relevância na Pesquisa
27.63%
We investigate wrinkling of two-dimensional random and triangular semiflexible polymer networks under shear. Both types of semiflexible networks exhibit wrinkling above a small critical shear angle, which scales with an exponent of the bending modulus between 1.9 and 2.0. Random networks exhibit hysteresis at the wrinkling threshold. Wrinkling lowers the total elastic energy by up to 20% and strongly affects the elastic properties of all semiflexible networks such as the crossover between bending and stretching dominated behavior. In random networks, we also find evidence for metastable wrinkled configurations. While the disordered microstructure of random networks affects the scaling behavior of wrinkle amplitudes, it has little effect on wrinkle wavelength. Therefore, wrinkles represent a robust, microstructure-independent assay of shear strain or elastic properties.; Comment: including supplemental material

Wrinkling of microcapsules in shear flow

Finken, Reimar; Seifert, Udo
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 25/01/2006
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27.51%
Elastic capsules can exhibit short wavelength wrinkling in external shear flow. We analyse this instability of the capsule shape and use the length scale separation between the capsule radius and the wrinkling wavelength to derive analytical results both for the threshold value of the shear rate and for the critical wave-length of the wrinkling. These results can be used to deduce elastic parameters from experiments.; Comment: 4 pages, 2 figures, submitted to PRL

A semi-analytical model for the wrinkling of laminates during consolidation over a corner radius

Dodwell, Timothy J.; Butler, Richard; Hunt, Giles W.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 14/05/2013
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27.51%
If carbon fibre layers are prevented from slipping over one another as they consolidate onto a non-trivial geometry, they can be particularly susceptible to wrinkling/buckling instabilities. A one dimensional model for wrinkling during consolidation over an external radius is presented. Critical conditions for the appearance of wrinkles provide possible manufacturing and design strategies to minimise wrinkling. Numerical results for the unstable post buckling paths show localized buckling behaviour which demonstrates qualitative agreement with micrographs of wrinkles.; Comment: 9 Pages, 8 figures, submitted to Composite Science and Technology May 2013

Wrinkling in polygonal membranes

Bonin, Arnaud Stephane
Fonte: University of Cambridge; Department of Engineering Publicador: University of Cambridge; Department of Engineering
Tipo: Thesis; doctoral; PhD
Relevância na Pesquisa
27.72%
Larger telescopes are required by astronomers to see further into the depths of our Universe, in order to understand its origins and the origins of life. A solution is to replace conventional primary mirrors in space-telescopes by membrane reflectors, that can be folded and fitted into a spacecraft before launch. Once deployed, the membrane would provide a large reflective surface necessary to obtain images of faraway celestial objects. Whilst the primary mirror of a space-telescope needs to have a very precise shape, membranes can have an uncertain shape for they are prone to wrinkling. For this reason, there is hesitation in using these structures for telescopes, as the technology needs to mature. In this thesis, regular polygonal membranes tensioned at their vertices are proposed as reflectors; their discrete nature necessitates a lighter support structure compared to circular membranes. Analysis has been made to assess the effect of the wrinkling in these polygonal membranes, where the primary focus has been on nominally flat membranes, alongside parabolic membranes. The area of reflectance of the membrane must be maximal and it is vital to mitigate wrinkles. In this thesis, the origins of the wrinkles are investigated and two novel stress analysis methods for polygonal membranes are developed initially. The first uses Airy stress functions: by superposing a number of these functions...