Transformation of Liposomes: Mechanical Behavior and Stability

1993 ◽  
Vol 46 (11S) ◽  
pp. S289-S294
Author(s):  
D. Pamplona
Keyword(s):  
Critical Pressure ◽  
Fluid Layer ◽  
Biological Membrane ◽  
Finite Elasticity ◽  
Spherical Shape ◽  
Thin Shells ◽  
Side View ◽  
Front View ◽  
The Stability ◽  
Morphological Transformations

Liposomes are small artificial vesicles of lipid bilayer, wich enclose and are surrounded by water. Morphological transformations in liposomes, starting from a spherical shape, due to changes in the osmotic pressure, have been described in the literature. The first transformation is into a circular biconcave form, afterwards the biconcave side view is maintained, while the front view reveals transformations into elliptical or regular polygonal forms, usually triangular, square or pentagonal. Finite elasticity and the theory of thin shells were used to analyse the behavior of the liposomes under decreasing volume. The biological membrane was considered as a two dimensional fluid layer, exhibiting solid properties to some extent, e.g., elasticity. The stability of the liposmes was studied by using the method of elastic perturbation to obtain the critical pressure for the biconcave transformation and the long liposome tubes. The transformations to elliptical and regular polygonal forms were studied using the linear stability equations of elasticity.

scholarly journals The elastic stability of an annular plate

1924 ◽  
Vol 106 (737) ◽  
pp. 268-284 ◽  
Keyword(s):  
Annular Plate ◽  
Practical Interest ◽  
Middle Surface ◽  
Elastic Stability ◽  
Thin Plates ◽  
Thin Shells ◽  
Stability Equation ◽  
Inner Radius ◽  
Plane Plate ◽  
The Stability

1. Introduction and Summary. —This paper deals with the elastic stability of a circular annular plate under uniform shearing forces applied at its edges. Investigations of the stability of plane plates are altogether simpler than those necessary in the case of curved plates or shells. In the first place, as shown by Mr. R. V. Southwell, two of the three equations of stability relate to a mode of instability that is not of practical interest, and are entirely independent of the third equation which gives the ordinary mode of instability resulting in the familiar bending of the middle surface of the plate. Consequently with a plane plate there is only one equation of stability to be solved, as contrasted with the case of a shell where the three equations are dependent, and must all be solved. In the second place the theory of thin shells can be used with confidence in a plane plate problem, though a more laborious procedure is necessary to deal adequately with a shell. The only stability equation required for the annular plate is therefore deduced without trouble from the theory of thin shells, and its solution presents no difficulty in the case of uniform shearing forces. A numerical discussion is given of the stability of the plate under such forces, the “favourite type of distortion” and the stess that will produce it being obtained for plates with clamped edges in wich the ratio of the outer to the inner radius exceeds 3·2. To some extent to results have been checked by experiment, in which part of the work the viter is indebted to Prof. G. I. Taylor for his valuable help and advice. Distrtion of the type predicted by the theory took place in the two thin plates of rober different ratio of radii, which were used. The disposition of the loci of points which undergo maximum normal displace nt gives some idea of the appearance of the plate after distortion has taken pce. The points have been calculated for a plate in which the ratio of radii 4·18, and the loci are shown on a diagram, which may be compared with a potograph of a distorted plate in which this ratio is 4·3. The ratio of normal dplacements of points of the plate can be seen from contours drawn on the ne diagram. (See pp. 280, 281.)

Notes on some Sculptures in the Acropolis Museum

1939 ◽  
Vol 39 ◽  
pp. 99-105
Author(s):  
C. Karouzos
Keyword(s):  
The Body ◽  
Side View ◽  
Front View

Payne's work on the Acropolis has given us a new picture of early Attic sculpture—a fresh and dewy garland, one of the finest flowers of which is his revelation of the personality of a supreme artist, the creator of the peplos Kore 679, the Rampin rider, the head 654 (Payne, Archaic Marble Sculpture from the Acropolis, pls. 11, 11a–c, 29–33, 133) and—πρὸς δὲ τόδε μέγα θαῦμα: the finest of all archaic Attic reliefs, the diskophoros Nat. Mus. 38. This last work is not included in Payne's list: and so, convinced though I am that the mere mention of this attribution is sufficient to establish it, I am bound to offer arguments in its support.Let us compare it with the work which stands chronologically closest to it, the head 654. We must keep in mind that, at that period, a relief was not simply a projection on the slab of the side view of the body, but a free composition of the side and front view. We must therefore compare all the aspects of the head 654 in turn with the diskophoros.

Chaotic mode competition in parametrically forced surface waves

1985 ◽  
Vol 158 ◽  
pp. 381-398 ◽  
Author(s):  
S. Ciliberto ◽  
J. P. Gollub
Keyword(s):  
Fluid Layer ◽  
Chaotic Regime ◽  
Mode Competition ◽  
Sampling Techniques ◽  
Onset Of Chaos ◽  
Chaotic Mode ◽  
The Stability ◽  
Degenerate Modes ◽  
Local Sampling ◽  
Slow Timescale

Vertical forcing of a fluid layer leads to standing waves by means of a subharmonic instability. When the driving amplitude and frequency are chosen to be near the intersection of the stability boundaries of two nearly degenerate modes, we find that they can compete with each other to produce either periodic or chaotic motion on a slow timescale. We utilize digital image-processing methods to determine the time-dependent amplitudes of the competing modes, and local-sampling techniques to study the onset of chaos in some detail. Reconstruction of the attractors in phase space shows that in the chaotic regime the dimension of the attractor is fractional and at least one Lyapunov exponent is positive. The evidence suggests that a theory incorporating four coupled slow variables will be sufficient to account for the mode competition.

scholarly journals CLINICAL AND ANATOMICAL RESTORATION OF THE MASTICATORY GROUP OF TEETH WITH A BURDENED GENERAL STATUS

2019 ◽  
Vol 23 (5) ◽  
pp. 202-207
Author(s):  
E. O Kudasova ◽  
N. I Kagramanova ◽  
Ekaterina Vladimirovna Kochurova ◽  
L. V Gavrushova ◽  
V. N Nikolenko ◽  
...  
Keyword(s):  
Base Material ◽  
Spherical Shape ◽  
Gastrointestinal Diseases ◽  
Secondary Caries ◽  
Dental Examination ◽  
Filling Materials ◽  
Hard Tissues ◽  
The Stability ◽  
Group B ◽  
The Cost

Objective. The chewing group of teeth is intended for equally crusher of food and forming food lump. This group is presented by two kinds of teeth: premolars and molars, and more often affected by caries, because a lot of retention zones are contribute to the active delay of plaque and the appearance of carious cavities. It is happening before 18 years. In the absence of these teeth or badly damaged of the crown part, food is chewed badly and as a result, stomach contain extremely large pieces. But its size is impossible for physiological digestion by the gastrointestinal tract and as a consequence the occurrence of gastrointestinal diseases. According to modern data, to work with lesions of hard tissues of the teeth, namely the chewing group of teeth, it is advisable to use composite light-curing microhybrid materials, which are characterized by particles close to the spherical shape. The aim of this study is determination of the possibility using a budgetary aesthetic composite for restorative restoration of the masticatory group of teeth in patients with a burdened anamnesis. Material and methodology. Was examined 22 people with aesthetic and anatomical disorders of the vestibular and occlusal surface of the hard tissues of the chewing group of teeth (n=154), followed by their recovery. The stability of filling materials was assessed according to Ryge-criteria: color coincidence, discoloration of the marginal segment, marginal adaptation, anatomical shape integrity, restoration surface, secondary caries. Results. Clinical and dental examination showed all the above violations of existing restorations (according to Ryge classification) in patients before restoration manipulations. After 1 week after the restoration, the examination showed that both groups of composites completely restore the anatomical and aesthetic chewing group of teeth and meet all the criteria. After 3 months, the assessmen t of the restoration by the composite of group A and group B did not reveal evidence of secondary caries on the perimeter of the restorations. Clinical and dental examination after 6 months showed minor changes in the restorations of composites of both groups in assessing the stability of color (90.9% and 83.3% in groups A and B) and the stability of surface polishing (89.6% and 81.8%, respectively). Discussion. The main signs of the restoration, which are undergoing changes, are discoloration, as well as the preservation of the smoothness of the surface regardless of the cost and branding of the base material.

scholarly journals Synthesis of Silver Nanoparticles from Anagalis arvensis and Their Biomedical Applications

2018 ◽  
Author(s):  
Mohib Shah ◽  
Natasha Anwar ◽  
Samreen Saleem ◽  
Iqbal Munir ◽  
Niaz Ali Shah ◽  
...  
Keyword(s):  
Silver Nanoparticles ◽  
Reducing Power ◽  
Spherical Shape ◽  
Artemia Salina ◽  
Maximum Activity ◽  
Tem Analysis ◽  
Synthesis Of Nanoparticles ◽  
The Stability ◽  
Average Size ◽  
Biological Methods

Background. Nanotechnology is promising field for generating new applications. A green synthesis of nanoparticles through biological methods using plant extract have a reliable and ecofriendly approach to improve our global environment. Methods. Silver nanoparticles (AgNPs) were synthesized using aqueous extract of Anagalis arvensis L and silver nitrate and were physicochemically characterized. Results. The stability of AgNPs toward acidity, alkalinity, salinity and temperature showed that they remained stable at room temperature for more than two months. The SEM and TEM analysis of the AgNPs showed that they have a uniform spherical shape with an average size in the range of 40–78 nm. Further 1-Dibhenyl-2-Picrylhydrazl radical in Anagalis arvensis L.mediated AgNPs showed a maximum activity of 98% at concentration of 200μg/mL. Hydrogen peroxide scavenging assay in Anagalis arvensis L. mediated AgNPs showed a maximum activity of 85% at concentration of 200μg/mL. Reducing power of Anagalis arvensis L.Ag NPs exhibited a higher activity of 330 μg/mL at concentration of 200 μg/mL. These NPs have cytotoxic effects against brine shrimp (Artemia salina) nauplii with a value of 53% LD 178.04μg/mL. Conclusion. The AgNPs synthesized using Anagalis arvensis L. extract demonstrate a broad range of applications.

The Stability of Natural Convection in an Inclined Fluid Layer in the Presence of AC Electric Field

1996 ◽  
Vol 65 (8) ◽  
pp. 2479-2484 ◽  
Author(s):  
Mohamed A. K. El Adawi ◽  
El Sayed F. El Shehawey ◽  
Safaa A. Shalaby ◽  
Mohamed I. A. Othman
Keyword(s):  
Natural Convection ◽  
Electric Field ◽  
Fluid Layer ◽  
Ac Electric Field ◽  
Inclined Fluid Layer ◽  
The Stability
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