On the fit of skins with a particular focus on the biomechanics of loose skins of hagfishes

2020 ◽  
Vol 98 (12) ◽  
pp. 827-843 ◽  
Author(s):  
T.A. Uyeno ◽  
A.J. Clark
Keyword(s):  
Local Buckling ◽  
Longitudinal Axis ◽  
Resistance Testing ◽  
Functional Categories ◽  
Puncture Resistance ◽  
Inflated Balloon ◽  
Freedom Of Movement ◽  
Length Changes ◽  
Skin Function ◽  
Low Pressures

There is a considerable diversity in how skins fit. Here, we review the function of both tight and loose skins and note that the latter are poorly understood. Analysis of loose skin examples suggest five functional categories: (I) freedom of movement, (II) surface area enhancement, (III) increased structural extensibility, (IV) lubrication, and (V) maladaptive examples arising through sexual or artificial selection. We investigate the skins of hagfishes as a model for understanding loose skin function by examining its structure using histology, standardized puncture resistance testing using the ASTM F1306 protocol, and the effect of internal pressure using a simple inflated balloon model. Skins of hagfishes are composed of multiple layers of cross-helically wound connective tissue fibers of a 45° angle to the longitudinal axis, resulting in a skin that functions as fabric cut “on the bias”. Hagfish skins are relatively yielding; however, skin looseness adds a “structural extensibility” that may allow hagfishes to compensate for low puncture resistance. Physical balloon models, with stiff cores that limit length changes, show that only low pressures allow short loop radii without local buckling. Hagfishes represent ideal organisms for studying loose skin function because their skins seem to fit in all functionally adaptive categories.

scholarly journals The Effect of Probe Geometry on Rind Puncture Resistance Testing of Maize Stalks

2020 ◽  
Author(s):  
Douglas D. Cook ◽  
Kyler Meehan ◽  
Levan Asatiani ◽  
Daniel J Robertson
Keyword(s):  
Meta Analysis ◽  
Resistance Testing ◽  
Test Results ◽  
Lodging Resistance ◽  
Puncture Resistance ◽  
Analysis Of Results ◽  
Stalk Lodging ◽  
Penetration Tests ◽  
Shape And Size ◽  
Probe Geometry

Abstract Background: Stalk lodging (breaking of plant stems prior to harvest) is a major impediment to increasing agricultural yields of grain crops. Rind puncture resistance is commonly used to predict the lodging resistance of several crop species. However, there exist no standard operating procedures or suggested protocols for conducting rind penetration experiments. In addition, experimental details of rind penetration tests such as the shape and size of the penetrating probe are rarely reported in the literature. This has prevented meta-analysis of results and has likewise prevented key findings of past studies from being replicated. As a first step towards establishing an agreed upon measurement standard for rind puncture resistance this study investigates the effect of the puncturing probe’s geometry on test results.Results: Results demonstrate that probe geometry has a significant impact on test results. In particular, results showed that a 2mm diameter chamfered probe produced stronger correlations with stalk bending strength than a 1.5mm diameter pointed probe. The chamfered probe was also more strongly correlated with geometric features of the stalk that are known to influence stalk lodging resistance (e.g., rind thickness, diameter and section modulus). In addition, several alternative rind penetration metrics were investigated, and some were found to be superior to the most common rind penetration metric of maximum load. Conclusions:There is a need in the agricultural and plant science community to create agreed-upon operating procedures and testing standards related to mechanical traits of plant stems. In particular, a standardized probe geometry and insertion rate for rind penetration studies are needed to enable greater interoperability and meta-analysis of results. Probe shape and size should be reported in any study conducting rind penetration tests as these factors significantly impact test results.

scholarly journals STRAIN-STRESS EXPERIMENTAL BEHAVIOUR OF TAPERED COLUMNS IN SINGLE-SPAN FRAMES/TRAPECINIŲ KOLONŲ VIENANAVIUOSE RĖMUOSE DEFORMACIJŲ-ĮTEMPIŲ BŪVIS

2000 ◽  
Vol 6 (2) ◽  
pp. 82-86 ◽  
Author(s):  
Vaidotas Šapalas
Keyword(s):  
Local Buckling ◽  
Longitudinal Axis ◽  
Lateral Torsional Buckling ◽  
Torsional Buckling ◽  
Perpendicular Plane ◽  
Strain Stress ◽  
Tapered Columns ◽  
The Stability ◽  
Experimental Behaviour ◽  
Tapered Column

Two single-span frame tests were carried out. The width of frame is 6m, column's height 4.17m. Frame supports are pinned. Connection between column and beam is rigid. Beam of the frame was loaded with two vertical and one horizontal loads. The stability of tappered columns was analysed in frame plane and in perpendicular plane, according to [1] and [2] methods. All deflections were calculated taking into account support movements. During the first frame test R1-1 the tapered column collapsed at the load 2V=400kN and H=200 kN (vertical and horizontal loads). During the second test R1-2 the tapered column collapsed at the load 2V=390 kN and H=175 kN. In both tests columns collapsed in lateral-torsional buckling way. Because the column's web is very thin at the load 2V=300 kN and H=150 kN the column's web achieved local buckling. But the column was still carrying the load. During both tests at the load 2V=300 kN and H=150 kN the column began to twist in the middle of its height about the longitudinal axis and to bend about the weak axis. In test R1-1, the vertical experimental deflection (in point 6, see Fig 1 a) is about 17.5% smaller than the theoretical one. The horizontal experimental deflection (in point, see Fig 1 a) is about 11.6% smaller than the theoretical one. In test R1-2, vertical experimental deflection (in point 6, see Fig 1 a) is about 21.1% bigger than the theoretical one. The horizontal experimental deflection (in point, see Fig 1 a) is about 29.6% smaller than the theoretical one. In test R1-1, an experimental compression stresses in section A-A (see Fig 2) are about 11.2% smaller than the theoretical one. Experimental tension stresses in section A-A are about 8.65% smaller than the theoretical one. In test R1-2, an experimental compression stresses in section A-A is about 0.43% bigger than the theoretical one. An experimental tension strain in section A-A is about 1.73% smaller than the theoretical one.

Study the Behavior of Castellated Steel Column Encasing by Different Reactive Powder Concrete Thickness with Laced Reinforcement

2021 ◽  
Vol 895 ◽  
pp. 97-109
Author(s):  
Mustafa Mazin Ghazi ◽  
Ahmad Jabbar Hussain Alshimmeri
Keyword(s):  
Axial Load ◽  
Local Buckling ◽  
Axial Loading ◽  
Longitudinal Axis ◽  
Load Test ◽  
Reactive Powder Concrete ◽  
Control Group ◽  
Load Carrying ◽  
Steel Column ◽  
Reactive Powder

Castellated columns are structural members that are created by breaking a rolled column along the center-line by flame after that rejoining the equivalent halves by welding such that for better structural strength against axial loading, the total column depth is increased by around 50 percent. The implementation of these institutional members will also contribute to significant economies of material value. The main objectives of this study are to study the enhancement of the load-carrying capacity of castellated columns with encasement of the columns by Reactive Powder Concrete (RPC) and lacing reinforcement, and serviceability of the confined castellated columns. The Castellated columns with RPC and Lacing Reinforcement improve compactness and local buckling (web and flange local buckling), as a result of steel section encasement. This study presents axial load test results for four specimens Castellated columns section encasement by Reactive powder concrete (RPC) with laced reinforcement. The encasement consists of, flanges unstiffened element height was filled with RPC for each side and laced reinforced which are used inclined continuous reinforcement of two layers on each side o0f the web of the castellated column. The inclination angle of lacing reinforcement concerning the longitudinal axis is 45o. Four specimens with four different configurations will be prepared and tested under axial load at columns. The first group was the control group (CSC1) Unconfined castellated steel column, the second group was consists of Castellated columns (web and flange) confined with 17mm of (RPC), welded web, and 6mm laced reinforcement (CSC3). While group three (CSC4) consists of a Castellated steel column same as the sample (CSC3), but without using welding between two parts of the castellated steel column. Groups four and five consist of a Castellated steel column same as sample (CSC4) encased partially with reactive powder concrete (25.5 mm) (CSC5) and full encased flange with reactive powder concrete (34mm) mm (CSC6), respectively. The tested specimens' results show that an increase in the strength of the column competitive with increasing the encased reactive powder concrete thickness. And the best sample was sample CSC6 with (34mm) mm in experimental and ABAQUS results.

Comparative Study of Structural Behavior for Asymmetrical Castellated (Concavely - Curved Soffit) Steel Beams with Different Strengthening Techniques

2021 ◽  
Vol 895 ◽  
pp. 177-189
Author(s):  
Ahmad Alaa Hussein ◽  
Ahmad Jabbar Hussain Alshimmeri
Keyword(s):  
Shear Strength ◽  
Reference Sample ◽  
Local Buckling ◽  
Bending Moment ◽  
Longitudinal Axis ◽  
Vertical Shear ◽  
Steel Beams ◽  
Horizontal Shear ◽  
Concentrated Loads ◽  
Reactive Powder

The Asymmetrical Castellated concavely – curved soffit Steel Beams with RPC and Lacing Reinforcement improves compactness and local buckling (web and flange local buckling), vertical shear strength at gross section (web crippling and web yielding at the fillet), and net section ( net vertical shear strength proportioned between the top and bottom tees relative to their areas (Yielding)), horizontal shear strength in web post (Yielding), web post-buckling strength, overall beam flexure strength, tee Vierendeel bending moment and lateral-torsional buckling, as a result of steel section encasement. This study presents two concentrated loads test results for seven specimens Asymmetrical Castellated concavely – curved soffit Steel Beams section encasement by Reactive powder concrete (RPC) with laced reinforcement. The encasement of the Asymmetrical Castellated concavely – curved soffit Steel Beams consists of, flanges unstiffened element height was filled with RPC for each side, and laced reinforced which are used inclined continuous reinforcement of two layers on each side of the Asymmetrical Castellated concavely – curved soffit Steel Beams web. The inclination angle of lacing reinforcement concerning the longitudinal axis is 45. Seven specimens with seven different configurations will be prepared and tested under two concentrated loads at the mid-third of the beam span. The tested specimen's properties are: unconfined Asymmetrical Castellated Steel Beams (Reference1), second model; Asymmetrical Castellated concavely – curved soffit Steel Beams (web and flange) confined with (RPC) only, third model; Asymmetrical Castellated concavely – curved soffit Steel Beams (web and flange) confined with (RPC) and laced reinforcement, fourth model; is same as the third model but it has one web opening with increase the depth of web post by 10 %, 20%, and 30 % as a gap between top and bottom parts of Asymmetrical Castellated concavely – curved soffit Steel Beams respectively. The results that have been obtained from the experimental part and the numerical analysis results by ABAQUS demonstrated that the increase of the gap leads to an increase in the load against the deflection curve. Sample CB8 with 122 mm gap has gained the highest load against deflection when compared with either reference sample without gap and other samples with 65 mm and 105 mm gap for concavely–curved soffit Steel Beams.

scholarly journals The effect of probe geometry on rind puncture resistance testing of maize stalks

Plant Methods ◽  
2020 ◽  
Vol 16 (1) ◽  
Author(s):  
Douglas D. Cook ◽  
Kyler Meehan ◽  
Levan Asatiani ◽  
Daniel J. Robertson
Keyword(s):  
Resistance Testing ◽  
Puncture Resistance ◽  
Maize Stalks ◽  
Probe Geometry

Design of Transversely Isotropic Tapered Plate Element in FRP Flexural Members

2005 ◽  
Vol 297-300 ◽  
pp. 2758-2766
Author(s):  
Sang Kyoon Jeong ◽  
Soon Jong Yoon ◽  
Won Sup Jang
Keyword(s):  
Slenderness Ratio ◽  
Ritz Method ◽  
Local Buckling ◽  
Longitudinal Axis ◽  
Graphical Form ◽  
Plate Element ◽  
Uniform Thickness ◽  
Buckling Mode ◽  
Aspect Ratios ◽  
Flexural Member

The structural shapes or plates with varying thickness are often adopted in aerospace industries such as a skin structure of an airplane and civil engineering fields where the load effects are varied along the longitudinal axis of the member. Specially, the structural steel tapered plate, so called LP (longitudinally profiled) plate, has been used in many countries as a part of main member of bridges, buildings, etc. This paper presents the result of an analytical study pertaining to the local buckling behavior of FRP (Fiber Reinforced Plastic) flexural member. The flexural member is consisted with uniform thickness web and flange tapered in thickness. The boundary conditions of flange plate in its unloaded edges are elastically restrained, but they are assumed to be either fixed-free or simple-free for simplicity. In the analysis, the Galerkin form of Rayleigh-Ritz method is adopted. The buckling equation of isolated unstiffened tapered plate elements having fixed-free or simple-free boundary condition in its unloaded edges is derived. The plate buckling coefficients with respect to the thickness ratios and plate aspect ratios are calculated and presented in a graphical form. Unlike the buckling of plate with uniform thickness, discontinuous changes of buckling mode are not exist. In addition, the critical slenderness ratio of such an unstiffened tapered plate element is suggested to prevent buckling.

scholarly journals The Patterns of Morphological Change During Intracerebral Hemorrhage Expansion: A Multicenter Retrospective Cohort Study

2022 ◽  
Vol 8 ◽  
Author(s):  
Chang Jianbo ◽  
Xiao Ting ◽  
Chen Yihao ◽  
Wang Xiaoning ◽  
Shang Hong ◽  
...  
Keyword(s):  
Intracerebral Hemorrhage ◽  
Morphological Change ◽  
Morphological Changes ◽  
Descriptive Analysis ◽  
Longitudinal Axis ◽  
Three Dimensions ◽  
Absolute Increase ◽  
Length Changes ◽  
Ct Data ◽  
Surface Regularity

Objectives: Hemorrhage expansion (HE) is a common and serious condition in patients with intracerebral hemorrhage (ICH). In contrast to the volume changes, little is known about the morphological changes that occur during HE. We developed a novel method to explore the patterns of morphological change and investigate the clinical significance of this change in ICH patients.Methods: The morphological changes in the hematomas of ICH patients with available paired non-contrast CT data were described in quantitative terms, including the diameters of each hematoma in three dimensions, the longitudinal axis type, the surface regularity (SR) index, the length and direction changes of the diameters, and the distance and direction of movement of the center of the hematoma. The patterns were explored by descriptive analysis and difference analysis in subgroups. We also established a prognostic nomogram model for poor outcomes in ICH patients using both morphological changes and clinical parameters.Results: A total of 1,094 eligible patients from four medical centers met the inclusion criteria. In 266 (24.3%) cases, the hematomas enlarged; the median absolute increase in volume was 14.0 [interquartile range (IQR), 17.9] mL. The initial hematomas tended to have a more irregular shape, reflected by a larger surface regularity index, than the developed hematomas. In subtentorial and deep supratentorial hematomas, the center moved in the direction of gravity. The distance of center movement and the length changes of the diameters were small, with median values of less than 4 mm. The most common longitudinal axis type was anterior–posterior (64.7%), and the axis type did not change between initial and repeat imaging in most patients (95.2%). A prognostic nomogram model including lateral expansion, a parameter of morphological change, showed good performance in predicting poor clinical outcomes in ICH patients.Conclusions: The present study provides a morphological perspective on HE using a novel automatic approach. We identified certain patterns of morphological change in HE, and we believe that some morphological change parameters could help physicians predict the prognosis of ICH patients.

Warm and freeze-fracture of cotton seed radicles

1987 ◽  
Vol 45 ◽  
pp. 984-985
Author(s):  
E. L. Vigil ◽  
E. F. Erbe
Keyword(s):  
Thin Film ◽  
Water Vapor ◽  
Fracture Surface ◽  
Membrane Structure ◽  
Room Temperature ◽  
Freeze Fracture ◽  
Longitudinal Axis ◽  
Fracture Plane ◽  
Cotton Seeds ◽  
Condensed Water

In cotton seeds the radicle has 12% moisture content which makes it possible to prepare freeze-fracture replicas without fixation or cryoprotection. For this study we have examined replicas of unfixed radicle tissue fractured at room temperature to obtain data on organelle and membrane structure.Excised radicles from seeds of cotton (Gossyplum hirsutum L. M-8) were fractured at room temperature along the longitudinal axis. The fracture was initiated by spliting the basal end of the excised radicle with a razor. This procedure produced a fracture through the tissue along an unknown fracture plane. The warm fractured radicle halves were placed on a thin film of 100% glycerol on a flat brass cap with fracture surface up. The cap was rapidly plunged into liquid nitrogen and transferred to a freeze- etch unit. The sample was etched for 3 min at -95°C to remove any condensed water vapor and then cooled to -150°C for platinum/carbon evaporation.

Electronmicroscopic localization of ribonucleic acids in ciliate Bursaria truncatella during cell division

1990 ◽  
Vol 48 (3) ◽  
pp. 132-133
Author(s):  
Vladimir Popenko ◽  
Natalya Cherny ◽  
Maria Yakovleva
Keyword(s):  
Cell Division ◽  
High Specificity ◽  
Longitudinal Axis ◽  
Gold Complexes ◽  
Somatic Nucleus ◽  
Ribonucleic Acids ◽  
Biological Meaning ◽  
Bivalent Cations ◽  
Lowicryl K4m ◽  
Short Time

Highly polyploid somatic nucleus (macronucleus) of ciliate Bursaria truncatella under goes severe changes in morphology during cell division. At first, macronucleus (Ma) condences, diminishes in size and turns perpendicular to longitudinal axis of the cell. After short time, Ma turns again, elongates and only afterwards the process of division itself occurs. The biological meaning of these phenomena is not clear.Localization of RNA in the cells was performed on sections of ciliates B. truncatella, embedded in “Lowicryl K4M” at various stages: (1) before cell division (Figs. 2,3); (11) at the stage of macronucleus condensation; (111) during elongation of Ma (Fig.4); (1111) in young cells (0-5min. after division). For cytochemical labelling we used RNaseAcolloidal gold complexes (RNase-Au), which are known to bind to RNA containing cell ularstructures with high specificity. The influence of different parameters on the reliability and reproducibility of labelling was studied. In addition to the factors, discussed elsewhere, we found that the balance of mono- and bivalent cations is of great significance.

New walls to keep the bad out: populism and the totalitarian psyche

2019 ◽  
Vol 1 (2) ◽  
pp. 120-130
Author(s):  
Coline Covington
Keyword(s):  
Cold War ◽  
Balance Of Power ◽  
Berlin Wall ◽  
Group Solidarity ◽  
Freedom Of Movement ◽  
Psychological Understanding ◽  
Psychic Development ◽  
The World ◽  
The Individual ◽  
The Cold War

The Berlin Wall came down on 9 November 1989 and marked the end of the Cold War. As old antagonisms thawed a new landscape emerged of unification and tolerance. Censorship was no longer the principal means of ensuring group solidarity. The crumbling bricks brought not only freedom of movement but freedom of thought. Now, nearly thirty years later, globalisation has created a new balance of power, disrupting borders and economies across the world. The groups that thought they were in power no longer have much of a say and are anxious about their future. As protest grows, we are beginning to see that the old antagonisms have not disappeared but are, in fact, resurfacing. This article will start by looking at the dissembling of a marriage in which the wall that had peacefully maintained coexistence disintegrates and leads to a psychic development that uncannily mirrors that of populism today. The individual vignette leads to a broader psychological understanding of the totalitarian dynamic that underlies populism and threatens once again to imprison us within its walls.

Sign in / Sign up

Export Citation Format

Share Document