scholarly journals Electromagnetically tunable cholesterics with oblique helicoidal structure [Invited]

2020 ◽  
Vol 10 (10) ◽  
pp. 2415
Author(s):  
Oleg D. Lavrentovich
Keyword(s):  
Helicoidal Structure

scholarly journals Mechanics-based analysis of selected features of the exoskeletal microstructure of Popillia japonica

2009 ◽  
Vol 24 (11) ◽  
pp. 3253-3267 ◽  
Author(s):  
Liang Cheng ◽  
Liyun Wang ◽  
Anette M. Karlsson
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Fiber Orientation ◽  
Fracture Resistance ◽  
Interfacial Strength ◽  
Maximum Tensile Stress ◽  
Popillia Japonica ◽  
Japanese Beetle ◽  
Mechanical Responses ◽  
Helicoidal Structure

We explore key mechanical responses of the layered microstructure found in selected parts of the exoskeletons (pronotum, leg and elytron) of Popillia japonica (Japanese beetle). Image analyses of exoskeleton cross-sections reveal four distinct layered regions. The load-bearing inner three regions (exocuticle, mesocuticle, and endocuticle) consist of multiple chitin-protein layers, in which chitin fibers align in parallel. The exocuticle and mesocuticle have a helicoidal structure, where the stacking sequence is characterized by a gradual rotation of the fiber orientation. The endocuticle has a pseudo-orthogonal structure, where two orthogonal layers are joined by a thin helicoidal region. The mechanics-based analyses suggest that, compared with the conventional cross-ply structure, the pseudo-orthogonal configuration reduces the maximum tensile stress over the exoskeleton cross-section and increases the interfacial fracture resistance. The coexistence of the pseudo-orthogonal and helicoidal structures reveals a competition between the in-plane isotropy and the interfacial strength in nature’s design of the biocomposite.

MEMBRANE FINITE ELEMENT FOR MODELING HEART WALL

2021 ◽  
Author(s):  
Miloš Kojić ◽  
Keyword(s):  
Finite Element ◽  
Complex Structure ◽  
Normal Stresses ◽  
Membrane Shell ◽  
Heart Motion ◽  
Wall Deformation ◽  
Helicoidal Structure ◽  
Conventional Models ◽  
And Function ◽  
Heart Wall

Modeling of heart wall deformation remains a challenge due to complex structure of tissue, which contains different group of cells and connective tissue. Muscle cells are dominant where, besides stresses coming from tissue deformation, active stresses are generated representing the load which produces heart motion and function. These cells form a helicoidal structure within so- called wall sheets and are considered as tissue fibers. Usual approach in the finite element (FE) discretization is to use 3D isoparametric elements. The dominant stresses lie in the sheet planes, while normal stresses in the wall normal directions are of the order smaller. Taking this stress state into account, we explore a possibility to model heart wall by membrane finite elements, hence considering the wall as a thick membrane (shell without bending effects). The membrane element is composite, containing layers over the thickness and variation of the direction of fibers. The formulated element is applied to a simplified left ventricle geometry to demonstrate a possibility to simulate heart mechanics by models which are much smaller and simpler for use than 3D conventional models.

A Biological System Producing a Self-Assembling Cholesteric Protein Liquid Crystal

1971 ◽  
Vol 8 (1) ◽  
pp. 93-109
Author(s):  
A. C. NEVILLE ◽  
B. M. LUKE
Keyword(s):  
Liquid Crystal ◽  
Electron Density ◽  
Electron Micrographs ◽  
Self Assembly ◽  
Liquid Crystalline ◽  
Density Variation ◽  
Self Assembling ◽  
The Matrix ◽  
Electron Density Variation ◽  
Helicoidal Structure

The protein in the oothecal glands of praying mantids (Sphodromantis tenuidentata, Miomantis monacha) exists in the form of lamellar liquid crystalline spherulites, which coalesce as they flow out of a punctured gland tubule. Electron micrographs of sections of these spherulites after fixation show parabolic patterns of an electron-light component, set in a continuous matrix of protein. Such patterns arise in helicoidal systems (e.g. arthropod cuticle) and microdensitometric scans of the matrix show a rhythmical electron-density variation consistent with helicoidal structure. Double spiral patterns identical to those seen in liquid crystal spherulites are illustrated. These properties resemble those of cholesteric liquid crystals. The constructional units appear to be molecular rather than fibrillar as described by previous authors. The helicoidal architecture arises by self-assembly in the gland lumen. Lamellar surface structures self-assembled spontaneously on glass coverslips when the protein was left to stand for several days. When heated to 55 °C, the birefringent liquid crystalline protein abruptly changes to an isotropic gel, with associated loss of parabolic patterning in electron micrographs and of the rhythmical electron-density variation on microdensitometric scans. This behaviour is compared to the formation of gelatin from collagen, in terms of the randomization of an originally ordered secondary structure.

An helicoidal structure surrounding the cilium axoneme: Visualization by the monoclonal antibody CC-248

1991 ◽  
Vol 71 (1-2) ◽  
pp. 191-200 ◽  
Author(s):  
Guillermina Bautista-Harris ◽  
Catherine Klotz ◽  
Nicole Bordes ◽  
Daniel Sandoz
Keyword(s):  
Monoclonal Antibody ◽  
Helicoidal Structure

scholarly journals Influence of alkyl chain length and fluorine atoms substitution on infrared spectra of chiral liquid crystalline esters

2017 ◽  
Vol 66 (3) ◽  
pp. 63-74
Author(s):  
Anna Drzewicz ◽  
Marzena Tykarska ◽  
Magdalena Żurowska
Keyword(s):  
Molecular Structure ◽  
Infrared Spectroscopy ◽  
Liquid Crystals ◽  
Infrared Spectra ◽  
Crystalline Phase ◽  
Liquid Crystalline ◽  
Alkyl Chain ◽  
Alkyl Chain Length ◽  
Rigid Core ◽  
Helicoidal Structure

The infrared spectra were registered for series of three-ring liquid crystalline esters, differing in the structure of alkyl chain, in the substitution of benzene ring by fluorine atoms and in the type of helicoidal structure in the chiral smectic CA phase with antiferroelectric properties. The influence of molecular structure on the shift of signals coming from carbonyl group, located in the rigid core, was observed. Keywords: liquid crystals, helicoidal structure, chiral smectic CA phase, antiferroelectric crystalline phase, infrared spectroscopy

scholarly journals Influence of molecular structure on helicoidal structure and NMR spectra of chiral liquid crystalline esters

2017 ◽  
Vol 66 (2) ◽  
pp. 25-35
Author(s):  
Anna Drzewicz ◽  
Marzena Tykarska ◽  
Mateusz Szala ◽  
Magdalena Żurowska
Keyword(s):  
Molecular Structure ◽  
Nmr Spectra ◽  
Liquid Crystalline ◽  
Room Temperature ◽  
Alkyl Chain ◽  
Light Reflection ◽  
13C Nmr Spectra ◽  
1H And 13C Nmr ◽  
Antiferroelectric Phase ◽  
Helicoidal Structure

Three-ring chiral liquid crystalline compounds, forming antiferroelectric phase, differing in the structure of alkyl chain and in the substitution of benzene ring by fluorine atoms were studied. The measurements of helical pitch, based on the selective light reflection phenomenon, were performed as well as 1H and 13C NMR spectra at room temperature were registered. The influence of molecular structure as well as the type of helicoidal structure on the chemical shift of signals coming from chiral center was observed. Keywords: liquid crystals, helicoidal structure, nuclear magnetic resonance, antiferroelectric phase

Helicoidal structure of the mixed ferrite-spinel Zn0.75Ni0.25Fe2O4

1979 ◽  
Vol 29 (5) ◽  
pp. 447-449 ◽  
Author(s):  
V.G. Vologin ◽  
S.F. Dubinin ◽  
V.D. Parkhomenko ◽  
S.K. Sidorov
Keyword(s):  
Mixed Ferrite ◽  
Helicoidal Structure ◽  
Ferrite Spinel

Helicoidal Structure of Paramyosin

Nature ◽  
1969 ◽  
Vol 224 (5224) ◽  
pp. 1105-1107 ◽  
Author(s):  
A. ELLIOTT ◽  
J. LOWY
Keyword(s):  
Helicoidal Structure
Sign in / Sign up

Export Citation Format

Share Document