scholarly journals Autotomy in plants: organ sacrifice in Oxalis leaves

2019 ◽  
Vol 16 (151) ◽  
pp. 20180737 ◽  
Author(s):  
Ilana Shtein ◽  
Alex Koyfman ◽  
Amram Eshel ◽  
Benny Bar-On
Keyword(s):  
South African ◽  
Invasive Plant ◽  
Body Part ◽  
Mechanical Analysis ◽  
Small Cells ◽  
African Origin ◽  
Whole Plant ◽  
Defence Strategy ◽  
Far Field Stress ◽  
The Sacrifice

Autotomy is a self-defence strategy of sacrificing a body part for survival. This phenomenon is widespread in the animal kingdom (e.g. gecko's tail) but was never reported in plants. In this study, we characterize the autotomy mechanism in the leaves of an invasive plant of South African origin, Oxalis pes-caprae. When the leaves and flowers of this plant are pulled, they break easily at their base, leaving the rest of the plant intact. Microscopic observations of the leaves reveal an area of small cells and a marked notch at this designated breaking point. Mechanical analysis showed that the strength statistics of the petioles follow Weibull's function. A comparison of the function parameters confirmed that strength of the tissue at that point is significantly smaller than at other points along the petiole, while the toughness of the tissue at the notch and at mid-petiole are approximately the same. We conclude that leaf fracture in Oxalis is facilitated by an amplification of the far-field stress in the vicinity of local, but abrupt, geometrical modification in the form of a notch. This presents an autotomy-like defence mechanism which involves the sacrifice of vital organs in order to prevent the uprooting of the whole plant.

scholarly journals High IgA antiphospholipid autoantibodies in healthy Sudanese explain the increased prevalence among Sudanese compared to Swedish systemic lupus erythematosus patients

Lupus ◽  
2020 ◽  
Vol 29 (11) ◽  
pp. 1412-1422 ◽  
Author(s):  
Sahwa Elbagir ◽  
Amir I Elshafie ◽  
Elnour M Elagib ◽  
NasrEldeen A Mohammed ◽  
Mawahib IE Aledrissy ◽  
...  
Keyword(s):  
Systemic Lupus Erythematosus ◽  
South African ◽  
Lupus Erythematosus ◽  
Fetal Loss ◽  
African Origin ◽  
Systemic Lupus ◽  
American College Of Rheumatology ◽  
Glycoprotein I ◽  
High Prevalence ◽  
Clinical Associations

Objectives IgA antiphospholipid antibodies (aPL) are prevalent in systemic lupus erythematosus (SLE) patients of African American, Afro-Caribbean and South African origin. Nevertheless, data from North Africa are lacking, and most studies use manufacturer-suggested cut-offs based on Caucasian controls. Therefore, we compared aPL isotypes in Sudanese and Swedish SLE patients using nation-based cut-offs. Methods Consecutive SLE patients and age- and sex-matched controls from Sudan ( N = 115/106) and Sweden ( N = 340/318) were included. All patients fulfilled the 1982 American College of Rheumatology SLE classification criteria. Antiphospholipid syndrome–related events were obtained from patients’ records. IgA/G/M anticardiolipin and anti-β2 glycoprotein I (β2GPI) were analysed with two independent assays. IgA anti-β2GPI domain 1 (D1) was also investigated. Manufacturers’ cut-offs and the 95th and 99th percentile cut-offs based on national controls were used. Results Sudanese patients and controls had higher levels and were more often positive for IgA aPL than Swedes when using manufacturers’ cut-offs. In contrast, using national cut-offs, the increase in IgA aPL among Sudanese patients was lost. Occurrence of IgA anti-D1 did not differ between the countries. Venous thromboses were less common among Sudanese patients and did not associate with aPL. No clinical associations were observed with IgA anti-β2GPI in Sudanese patients. Thromboses in Swedes were associated with IgG/M aPL. Fetal loss was associated with aPL in both cohorts. Conclusions IgA anti-β2GPI prevalence was higher among Sudanese compared to Swedish patients when manufacturers’ cut-offs were used. This situation was reversed when applying national cut-offs. Anti-D1 was not increased in Sudanese patients. Previous studies on populations of African origin, which demonstrate a high prevalence of IgA aPL positivity, should be re-evaluated using a similar cut-off approach.

scholarly journals A dynamic modelling tool to anticipate the effectiveness of invasive plant control and restoration recovery trajectories in South African Fynbos

2020 ◽  
Author(s):  
Stuart A. Hall ◽  
Rita Bastos ◽  
Joana Vicente ◽  
Ana Sofia Vaz ◽  
João P. Honrado ◽  
...  
Keyword(s):  
South African ◽  
Invasive Plant ◽  
Dynamic Modelling ◽  
Plant Control

scholarly journals Investigation of the acaricidal activity of the acetone and ethanol extracts of 12 South African plants against the adult ticks of Rhipicephalus turanicus

2017 ◽  
Vol 84 (1) ◽  
Author(s):  
Gerda Fouche ◽  
Bellonah M. Sakong ◽  
Olubukola T. Adenubi ◽  
Jean Paul Dzoyem ◽  
Vinny Naidoo ◽  
...  
Keyword(s):  
South African ◽  
Ethanol Extract ◽  
Immersion Test ◽  
Acaricidal Activity ◽  
Contact Method ◽  
Cleome Gynandra ◽  
Whole Plant ◽  
African Plants ◽  
Ethanol Extracts ◽  
Acetone Extracts

The acaricidal activity of acetone and ethanol extracts of 12 plant species was evaluated using the contact method on Rhipicephalus turanicus (Acari: Ixodidae) ticks at an initial concentration of 20% (200 mg/mL). Eight of the 12 plants had mortality greater than 50% and the acetone extracts had better acaricidal activity than the ethanol extracts. The acetone extract of Calpurnia aurea (leaves and flowers) had the highest corrected mortality (CM) of 92.2% followed by Schkuhria pinnata (whole plant) with a CM of 88.9%, Ficus sycomorus (bark and stems) 86.7% and Senna italica subsp. arachoides (roots, leaves and fruits) 83.3%. Selected extracts were tested at five different concentrations using the adult immersion test. From dose–response assays, EC<sub>50</sub> values of 61.82 mg/mL, 115.21 mg/mL and 161.02 mg/mL were obtained for the acetone extracts of S. pinnata (whole plant), S. italica subsp. arachoides (roots, leaves and fruits) and C. aurea (leaves and flowers) respectively. The ethanol extract of Monsonia angustifolia (whole plant) had the highest CM of 97.8% followed by S. pinnata (whole plant) with a CM of 86.7%, C. aurea (leaves and flowers) 81.1% and Cleome gynandra (leaves) 77.8%. There is potential for the development of environmentally benign botanicals as natural acaricides against R. turanicus.

Micro-Mechanical Analysis of Composites Reinforced with Discontinuous Fibers with Large Aspect Ratio

2013 ◽  
Vol 420 ◽  
pp. 269-275
Author(s):  
Milan Žmindák ◽  
Martin Dudinsky ◽  
Zoran Pelagić
Keyword(s):  
Aspect Ratio ◽  
Glass Fibers ◽  
Fiber Composites ◽  
Mechanical Analysis ◽  
Basis Functions ◽  
Large Aspect Ratio ◽  
Domain Boundaries ◽  
Linear Problems ◽  
Far Field Stress ◽  
Continuous Source

Properties of fiber composites reinforced with fibers greatly depend on the choice of fiber and matrix. Their mechanical properties and geometry influence the stress state in composite. In this paper the Method of Continuous Source Functions (MCSF) employing Trefftz Radial Basis Functions (TRBF) is presented. This method does not require any mesh. The focus will be given to the application of TRBF in form of dipoles to the simulation of composites reinforced with fibers of finite length with large aspect ratio. In presented example as well as in other linear problems, only nodes on the domain boundaries and a set of source functions in points outside the solution domain are necessary to satisfy the boundary conditions. Finally employing of MCSF for analysis of patch of glass fibers embedded in epoxy matrix subjected to far field stress is shown.

Composting Invasive Plants in the Rio Grande River

2014 ◽  
Vol 7 (3) ◽  
pp. 473-482 ◽  
Author(s):  
Erica J. Meier ◽  
Tina M. Waliczek ◽  
Michael L. Abbott
Keyword(s):  
Invasive Species ◽  
Plant Species ◽  
Large Scale ◽  
Invasive Plant ◽  
Giant Reed ◽  
Invasive Plant Species ◽  
Whole Plant ◽  
Germination And Growth ◽  
Vegetative Propagules ◽  
The U.S

AbstractThe purpose of this study was to determine the effect of whole-plant composting on the viability of seeds and other propagules of the invasive plant species waterhyacinth, waterlettuce, hydrilla, and giant reed while producing a valuable compost product. Invasive species were subjected to preliminary germination and growth tests and oven mortality tests to evaluate whether species distribution was via seeds, vegetative propagules, or both, as well as whether the composting process had the potential, through the high temperatures obtained, to kill seeds and other propagules. Germination and growth tests determined the means by which invasive species spread. Oven tests determined the temperatures at which unscarified and scarified seeds and propagules were rendered inviable. Achieving temperatures of at least 57.2 C was necessary within constructed compost piles to effectively kill the plants without the danger of redistribution. In the field, the study successfully developed a large-scale composting operation using invasive plant species as the primary feedstock. Analysis of field-scale composting showed final materials were within satisfactory to ideal levels for samples analyzed by the U.S. Compost Council's Seal of Testing Assurance Program and were, therefore, a valuable compost product.

scholarly journals Evaluation of 100 most cited research articles on African medicinal plants

2021 ◽  
Vol 8 (2) ◽  
Author(s):  
Kunle Okaiyeto ◽  
Oluwafemi O Oguntibeju
Keyword(s):  
Medicinal Plants ◽  
South African ◽  
Addis Ababa ◽  
Collaboration Network ◽  
African Origin ◽  
Therapeutic Uses ◽  
Kwazulu Natal ◽  
Prolific Authors ◽  
The University ◽  
African Journal

The mission for drug discovery and progress has prompt researchers to scientifically validate the therapeutic uses of medicinal plants available worldwide, of which, African medicinal plants serve as a great reservoir. Despite the extensive work in the field of medicinal plants of African origin, however, bibliometric report on the work conducted on African medicinal plants is scarce, and hence, the present study aimed at evaluating the top 100 most cited articles on medicinal plant wealth of Africa. The literature data used for the bibliometric analysis was explored from Web of Science (WoS) while RStudio and VOSviewer software were used for data analysis and collaboration network visualization, respectively. The most prolific authors were Van Staden J, Jager AK, Teklehaymanot T whereas, the top 3 journals were Journal of Ethnopharmacology, Journal of Ethnobiology and Ethnomedicine, and South African Journal of Botany. Most cited journals were Journal of Ethnopharmacology, Phytochemistry, Phytotherapy Research. The topmost institutions in terms of the number of articles were the University of KwaZulu-Natal, University of Addis Ababa and Pretoria. South Africa was the most cited country followed by Nigeria. Single country publications dominated the field and therefore, multiple country collaboration should be a focus of social networks among the researchers in the field.

Non-Linear Vibration of Rotating Co-Rotational Two-Dimensional Beams With Large Displacement

2018 ◽  
Author(s):  
Zihan Shen ◽  
Benjamin Chouvion ◽  
Fabrice Thouverez ◽  
Aline Beley ◽  
Jean-Daniel Beley
Keyword(s):  
Rigid Body ◽  
Large Deformation ◽  
Local Coordinate System ◽  
Geometrical Nonlinearity ◽  
Body Part ◽  
Mechanical Analysis ◽  
Body Motion ◽  
Large Displacements ◽  
Geometrical Nonlinearities ◽  
Gyroscopic Effects

In order to achieve better performances and reduce fuel consumption, the new generation of turbomachines uses larger and lighter design, for instance the “open-rotor” concept, and is conceived to rotate at higher speeds. Parts of the structure become then even more likely to undergo large amplitude vibrations. Consequently, the conception of future aero-engine requires a sound and robust technique to predict the rotating machine vibrations considering geometrical nonlinearities (large displacements and large deformation). In this paper, the nonlinear vibrations of rotating beams with large displacements is investigated by the use of the Co-Rotational (C-R) finite element method. In the C-R approach, the full motion of each element is decomposed into a rigid body part and a pure deformational part by introducing a local coordinate system attached to the element. The utilization of the C-R method offers the possibility to treat geometrical nonlinearity directly with pre-extracted rigid body motion displacements. The originality we propose in this study is to derive its formulation in a rotating reference frame and include both centrifugal and gyroscopic effects. The nonlinear governing equations are obtained from Lagrange’s equations using a consistent expression for the kinetic energy. With this formulation, the spin-stiffening effect from geometrical nonlinearities due to large displacements is accurately handled. The proposed approach is then applied to several types of mechanical analysis (static large deformation, modal analysis at different spin speeds, and transient analysis after an impulsive force) to verify its accuracy and demonstrate its efficiency.

scholarly journals Cross-cultural equivalence of the organisational culture survey in Australia

2001 ◽  
Vol 27 (3) ◽  
Author(s):  
R. Erwee ◽  
B. Lynch ◽  
B. Millet ◽  
D. Smith ◽  
G. Roodt
Keyword(s):  
South African ◽  
Organisational Culture ◽  
Cross Cultural ◽  
African Origin ◽  
Logical Positivist ◽  
Australian Institute ◽  
Australian Context ◽  
Recent Trends ◽  
Conceptual Equivalence ◽  
Clear Statement

The aim of this study is to assess whether the cross-cultural equivalence of the Organisational Culture Survey (OCS) persist in an Australian context. The nature of the instrument is presented which includes a clear statement of its South African origin and its’ place within a logical positivist paradigm. The sample consisted of 326 respondents from a population of managers of the Australian Institute of Management. This study confirms the instrument’s validity and internal consistency within an Australian context, but that further research is required into the functional and conceptual equivalence of the survey items and dimensions underpinning the items to conclusively establish its utility. Finally, aspects of the ‘organisational culture’ construct underlying the survey need revision given recent trends in related systems, complexity and chaos theories.OpsommingTechnikons propageer die beoefening van ko˛peratiewe onderwys,’n opvoedkundige strategiewat leer deur produktiewewerkservaring integreermet die teoretiese kurrikulum. ByTechnikon SAegter, het slegs sowat 35% van die formele programme ’n verpligte leerervarings komponent.Teoretiese-begrondings navorsingsmetodologie is gebruik omsekere basiese veronderstellings van akademiese personeel te bepaal. Eerder as om’n spesifieke navorsingsprobleemas vertrekpunt te gebruik, ondersoek teoretiese-begronding’n areavan belang en laat die metodiek die relevante sake toe omte voorskyn te kom. Semi-gestruktureerde onderhoude,met vier ope vrae, is gevoer met ’n gestratifiseerde eweskansige steekproef van 25 akademiese personeellede vanTechnikon SA. Daar is bevind dat alhoewel daar beperkte oortuiging en gewillige uitlewing van kooperatiewe onderwys is, is dit nie beduidend as kenmerkend van die organisasie kultuur vanTechnikon SA nie.

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