The scientific merit of Carpobrotus mellei L. based on antimicrobial activity and chemical profiling

Species of the genus Carpobrotus are similar in appearance and have been used for medicinal purposes over many generations. Carpobrotus mellei is endemic to the south-Western Cape of South Africa, and also used for various ailments. To date no scientific validation and information has been reported on C. mellei. This study investigated the antimicrobial potential of C. mellei against Staphylococcus aureus, Pseudomonas aeruginosa, Candida albicans and Mycobacterium smegmatis, and determined the minimum inhibitory concentrations (MIC) by two-fold serial dilution. C. mellei showed antimicrobial activity against S. aureus and M. smegmatis in the disc diffusion method. Eight chemical compounds showed clear zones of inhibition in the bioautograms, seven against S. aureus and three compounds were active against M. smegmatis. The ethyl acetate extracts have MIC values of 7.5 mg/ml and 15 mg/ml against S. aureus and M. smegmatis, respectively. Phytochemical tests indicated the presence of flavonoids, hydrolysable tannins, phytosterols and aromatic acids. High performance liquid chromatography (HPLC) showed a species-specific spectrum at a wavelength of 280 nm. The results confirm that C. mellei has scientific merit, and can substitute one of the other Carpobrotus species for antimicrobial usage within the south-Western Cape of South Africa

Effect of Cissampelos capensis rhizome extract on human spermatozoa in vitro

Cissampelos capensis is commonly known by the Afrikaans name ‘dawidjies’ or ‘dawidjieswortel’. C. capensis is the most important and best-known medicinal plant of the family Menispermaceae used by the Khoisan and other rural people in the western regions of South Africa. Among numerous other ailments, it is traditionally taken to treat male fertility problems. Yet, no studies have investigated the effects of this plant or its extracts on human spermatozoa. The aim of study was to investigate the effects of C. capensis extracts on sperm function. A total of 77 semen samples were collected. Spermatozoa were washed with HTF-BSA medium and incubated with different concentrations of C. capensis (0, 0.05, 0.5, 5, 50, 200 μg ml−1) for 1 h at 37 °C. Sperm motility, vitality, acrosome reaction, reactive oxygen species (ROS), capacitation, Annexin V binding, DNA fragmentation and mitochondrial membrane potential (Δψm) were determined. While viability, Annexin V positivity and Δψm were not affected, the percentages of ROS-positive, TUNEL-positive, capacitated and hyperactivated spermatozoa increased significantly and dose-dependently. It is concluded that the alkaloids present in the extract of C. capansis rhizomes triggered sperm intrinsic superoxide production leading to sperm capacitation and DNA fragmentation.Web of Scienc

Local shear transformations in deformed and quiescent hard-sphere colloidal glasses

We performed a series of deformation experiments on a monodisperse, hard-sphere colloidal glass while simultaneously following the 3D trajectories of roughly 50,000 individual particles with a confocal microscope. In each experiment, we deformed the glass in pure shear at a constant strain rate (1 − 5 × 10−5s−1) to maximum macroscopic strains (5 − 10%), then reversed the deformation at the same rate to return to zero macroscopic strain. We also measured 3D particle trajectories in an identically-prepared quiescent glass in which the macroscopic strain was always zero. We find that shear transformation zones exist and are active in both sheared and quiescent colloidal glasses, revealed by a distinctive four-fold signature in spatial autocorrelations of the local shear strain. With increasing shear, the population of local shear transformations develops more quickly than in a quiescent glass, and many of these transformations are irreversible. When the macroscopic strain is reversed, we observe partial elastic recovery, followed by plastic deformation of the opposite sign, required to compensate for the irreversibly transformed regions. The average diameter of the shear transformation zones at maximum strain is 2.3 particle diameters.Engineering and Applied Science

Stiffness of the Crystal-Liquid Interface in a Hard-Sphere Colloidal System Measured from Capillary Fluctuations

Face-centered cubic single crystals of $σ=1.55 μm$ diameter hard-sphere silica colloidal particles were prepared by sedimentation onto (100) and (110) oriented templates. The crystals had a wide interface with the overlaying liquid that was parallel to the template. The location of the interface was determined by confocal microscopic location of the particles, followed by identification of the crystalline and liquid phases by a bond-orientation order parameter. Fluctuations in the height of the interface about its average position were recorded for several hundred configurations. The interfacial stiffness $γ̃$ was determined from the slope of the inverse squared Fourier components of the height profile vs the square of the wave number, according to the continuum capillary fluctuation method. The offset of the fit from the origin could quantitatively be accounted for by gravitational damping of the fluctuations. For the (100) interface, $γ̃ =(1.3±0.3)k_{B}T/σ^{2}$; for the (110) interface, $γ̃ =(1.0±0.2)k_{B}T/σ^{2}$. The interfacial stiffness of both interfaces was found to be isotropic in the plane. This is surprising for the (110), where crystallography predicts twofold symmetry. Sedimentation onto a (111) template yielded a randomly stacked hexagonal crystal with isotropic $γ̃ =0.66k_{B}T/σ^{2}$. This value, however, is less reliable than the two others due to imperfections in the crystal.Engineering and Applied SciencesPhysic

Experimental Observation of the Crystallization of Hard-Sphere Colloidal Particles by Sedimentation onto Flat and Patterned Surfaces

We present a confocal microscopy study of 1.55micrometers monodisperse silica hard spheres as they sediment and crystallize at the bottom wall of a container. If the particles sediment onto a featureless flat wall, the two bottom layers crystallize simultaneously and layerwise growth follows. If the wall is replaced by a hexagonal template, only layerwise growth occurs. Our results complement earlier numerical simulations and experiments on other colloidal systems.Physic

Crystallization of undercooled liquid fenofibrate

Formulation of hydrophobic drugs as amorphous materials is highly advantageous as this increases their solubility in water and therefore their bioavailability. However, many drugs have a high propensity to crystallize during production and storage, limiting the usefulness of amorphous drugs. We study the crystallization of undercooled liquid fenofibrate, a model hydrophobic drug. Nucleation is the rate-limiting step; once seeded with a fenofibrate crystal, the crystal rapidly grows by consuming the undercooled liquid fenofibrate. Crystal growth is limited by the incorporation of molecules into its surface. As nucleation and growth both entail incorporation of molecules into the surface, this process likely also limits the formation of nuclei and thus the crystallization of undercooled liquid fenofibrate, contributing to the good stability of undercooled liquid fenofibrate against crystallization

Phytochemical screening and biological activity studies of five South African indigenous medicinal plants

Different extracts and fractions of five selected indigenous South African medicinal plants, namely, Cissampelos capensis, Geranium incanum and three Gethyllis species, were subjected to phytochemical screening and testing for cytotoxicity using the brine shrimp lethality bioassay, and antimicrobial activity assays against nine microbes, which included three fungal species, three Gram negative and three Gram positive bacteria.The majority of the extracts tested positive for the presence of tannins, phenolics and flavonoids, while in selected cases, phytochemical tests suggested the presence of essential oils, glycosides or alkaloids. The methanol extract of Gethyllis gregoriana displayed the highest cytotoxicity levels. Generally, the highest levels of biological activity were shown to reside in the methanolic extracts, while hexane extracts revealed very low to zero activity. The total tertiary alkaloid (TTA) of C. capensis was mostly active against Bacillus subtilis, a Gram +ve bacteria. The trends observed for the cytotoxicity assay were in agreement with those observed for the antimicrobial assay

Towards Principled Responsible Research and Innovation: Employing the Difference Principle in Funding Decisions

Responsible Research and Innovation (RRI) has emerged as a science policy framework that attempts to import broad social values into technological innovation processes whilst supporting institutional decision-making under conditions of uncertainty and ambiguity. When looking at RRI from a ‘principled’ perspective, we consider responsibility and justice to be important cornerstones of the framework. The main aim of this article is to suggest a method of realising these principles through the application of a limited Rawlsian Difference Principle in the distribution of public funds for research and innovation. There are reasons why the world's combined innovative capacity has spewed forth iPhones and space shuttles but not yet managed to produce clean energy or universal access to clean water. (Stilgoe 2013, xii) I derive great optimism from empathy's evolutionary antiquity. It makes it a robust trait that will develop in virtually every human being so that society can count on it and try to foster and grow it. It is a human universal. (de Waal 2009, 209) Responsible Research and Innovation (RRI) has emerged as a science policy framework that attempts to import broad social values into technological innovation processes whilst supporting institutional decision-making under conditions of uncertainty and ambiguity. In this respect, RRI re-focuses technological governance from standard debates on risks to discussions about the ethical stewardship of innovation. This is a radical step in Science & Technology (S&T) policy as it lifts the non-quantifiable concept of values into the driving seat of decision-making. The focus of innovation then goes beyond product considerations to include the processes and – importantly – the purposes of innovation (Owen et al. 2013, 34). Shared public values are seen as the cornerstone of the new RRI framework, while market mechanisms and risk-based regulations are of a secondary order. What are the values that could drive RRI? There are different approaches to the identification of public values. They can be located in democratically agreed processes and commitments (such as European Union treaties and policy statements) or they can be developed organically via public engagement processes. Both approaches have advantages and disadvantages. For instance, although constitutional values can be regarded as democratically legitimate, their application to specific technological fields can be difficult or ambiguous (Schroeder and Rerimassie 2015). On the other hand, public engagement can accurately reflect stakeholder values but is not necessarily free from bias and lobbyist agenda setting. We argue that if RRI is to be more successful in resolving policy dilemmas arising from poorly described and uncertain technological impacts, basic universal principles need to be evoked and applied. When looking at RRI from a ‘principled’ perspective, we consider responsibility and justice to be important cornerstones of the framework. One could describe them in the following manner: Research and innovation should be conducted responsibly. Publicly funded research and innovation should be focused fairly on socially beneficial targets. Research and innovation should promote and not hinder social justice. The main aim of this article is to suggest a method of realising these principles through the application of a limited Rawlsian Difference Principle in the distribution of public funds for research and innovation. This paper is in three parts. The first part discusses the above principles and introduces the Rawlsian Difference Principle. The second part identifies how RRI is currently applied by public funding bodies. The third part discusses the operationalisation of the Rawlsian Difference Principle in responsible funding decisions

Propagation of extended fractures by local nucleation and rapid transverse expansion of crack-front distortion

Fractures are ubiquitous and can lead to the catastrophic material failure of materials. Although fracturing in a two-dimensional plane is well understood, all fractures are extended in and propagate through three-dimensional space. Moreover, their behaviour is complex. Here we show that the forward propagation of a fracture front occurs through an initial rupture, nucleated at some localized position, followed by a very rapid transverse expansion at velocities as high as the Rayleigh-wave speed. We study fracturing in a circular geometry that achieves an uninterrupted extended fracture front and use a fluid to control the loading conditions that determine the amplitude of the forward jump. We find that this amplitude correlates with the transverse velocity. Dynamic rupture simulations capture the observations for only a high transverse velocity. These results highlight the importance of transverse dynamics in the forward propagation of an extended fracture