Comparison of the antibacterial activity of essential oils and extracts of medicinal and culinary herbs to investigate potential new treatments for irritable bowel syndrome

BACKGROUND:Irritable bowel syndrome (IBS) is a common functional gastrointestinal disorder, which may result from alteration of the gastrointestinal microbiota following gastrointestinal infection, or with intestinal dysbiosis or small intestinal bacterial overgrowth. This may be treated with antibiotics, but there is concern that widespread antibiotic use might lead to antibiotic resistance. Some herbal medicines have been shown to be beneficial, but their mechanism(s) of action remain incompletely understood. To try to understand whether antibacterial properties might be involved in the efficacy of these herbal medicines, and to investigate potential new treatments for IBS, we have conducted a preliminary study in vitro to compare the antibacterial activity of the essential oils of culinary and medicinal herbs against the bacterium, Esherichia coli.METHODS:Essential oils were tested for their ability to inhibit E. coli growth in disc diffusion assays and in liquid culture, and to kill E. coli in a zone of clearance assay. Extracts of coriander, lemon balm and spearmint leaves were tested for their antibacterial activity in the disc diffusion assay. Disc diffusion and zone of clearance assays were analysed by two-tailed t tests whereas ANOVA was performed for the turbidometric assays.RESULTS:Most of the oils exhibited antibacterial activity in all three assays, however peppermint, lemon balm and coriander seed oils were most potent, with peppermint and coriander seed oils being more potent than the antibiotic rifaximin in the disc diffusion assay. The compounds present in these oils were identified by gas chromatography mass spectrometry. Finally, extracts were made of spearmint, lemon balm and coriander leaves with various solvents and these were tested for their antibacterial activity against E. coli in the disc diffusion assay. In each case, extracts made with ethanol and methanol exhibited potent antibacterial activity.CONCLUSIONS:Many of the essential oils had antibacterial activity in the three assays, suggesting that they would be good candidates for testing in clinical trials. The observed antibacterial activity of ethanolic extracts of coriander, lemon balm and spearmint leaves suggests a mechanistic explanation for the efficacy of a mixture of coriander, lemon balm and mint extracts against IBS in a published clinical trial

Deposition of High Conductivity Low Silver Content Materials by Screen Printing

A comprehensive experimental investigation has been carried out into the role of film thickness variation and silver material formulation on printing capability in the screen printing process. A full factorial experiment was carried out where two formulations of silver materials were printed through a range of screens to a polyester substrate under a set of standard conditions. The materials represented a novel low silver content (45%–49%) polymer material and traditional high silver content (65%–69%) paste. The resultant prints were characterised topologically and electrically. The study shows that more cost effective use of the silver in the ink was obtained with the low silver polymer materials, but that the electrical performance was more strongly affected by the mesh being used (and hence film thickness). Thus, while optimum silver use could be obtained using materials with a lower silver content, this came with the consequence of reduced process robustness

A model for ink impression into a porous substrate

This paper applies the physics of a squeezed film between porous surfaces to the impression of an ink dot into paper. The models developed are implemented numerically via the finite-element method. When compared with observations reported in the literature, the models are shown to be capable of representing the effects of process parameters such as the pressure, viscosity, permeability and film thickness on the dot gain which is used frequently as a characteristic to measure printing quality

Rheology of high-aspect-ratio nanocarbons dispersed in a low-viscosity fluid

Printing inks typically consist of a functional component dispersed within a low-viscosity resin/solvent system where interparticle interactions would be expected to play a significant role in dispersion, especially for the high-aspect-ratio nanocarbons such as the graphite nanoplatelets (GNPs). Rheology has been suggested as a method for assessing the dispersion of carbon nanomaterials in a fluid. The effects of phase volume of ammonia plasma-functionalized GNPs on a near-Newtonian low-viscosity thermoplastic polyurethane (TPU) resin system have been studied using shear and quiescent oscillatory rheology. At low concentrations, the GNPs were well dispersed with a similar shear profile and viscoelastic behavior to the unfilled TPU resin, as viscous behavior prevailed indicating the absence of any long-range order within the fluid. Particle interactions increased rapidly as the phase volume tended toward maximum packing fraction, producing rapid increases in the relative viscosity, increased low shear rate shear thinning, and the elastic response becoming increasingly frequency independent. The nanoscale dimensions and high-aspect-ratio GNPs occupied a large volume within the flow, while small interparticle distances caused rapid increases in the particle–particle interactions to form flocculates that pack less effectively. Established rheological models were fitted to the experimental data to model the effect of high-aspect-ratio nanocarbon on the viscosity of a low-viscosity system. Using the intrinsic viscosity and the maximum packing fraction as fitting parameters, the Krieger–Dougherty (K–D) model provided the best fit with values. There was good agreement between the estimates of aspect ratio from the SEM images and the predictions of the aspect ratio from the rheological models. The fitting of the K–D model to measured viscosities at various phase volumes could be an effective method in characterizing the shape and dispersion of high-aspect-ratio nanocarbons

A Study of the Abrasion of Squeegees Used in Screen Printing and Its Effect on Performance with Application in Printed Electronics

This article presents a novel method for accelerated wear of squeegees used in screen printing and describes the development of mechanical tests which allow more in-depth measurement of squeegee properties. In this study, squeegees were abraded on the screen press so that they could be used for subsequent print tests to evaluate the effect of wear on the printed product. Squeegee wear was found to vary between different squeegee types and caused increases in ink transfer and wider printed features. In production this will lead to greater ink consumption, cost per unit and a likelihood of product failure. This also has consequences for the production of functional layers, etc., used in the construction of printed electronics. While more wear generally gave greater increases in ink deposition, the effect of wear differed, depending on the squeegee. There was a correlation between the angle of the squeegee wear and ink film thickness from a worn squeegee. An ability to resist flexing gave a high wear angle and presented a sharper edge at the squeegee/screen interface thus mitigating the effect of wear. There was also a good correlation between resistance to flexing and ink film thickness for unworn squeegees, which was more effective than a comparison based on Shore A hardness. Squeegee indentation at different force levels gave more information than a standard Shore A hardness test and the apparatus used was able to reliably measure reductions in surface hardness due to solvent absorption. Increases in ink deposition gave lower resistance in printed silver lines; however, the correlation between the amount of ink deposited and the resistance, remained the same for all levels of wear, suggesting that the wear regime designed for this study did not induce detrimental print defects such as line breakages

The effect of plasma functionalization on the print performance and time stability of graphite nanoplatelet electrically conducting inks

Carbon-based pastes and inks are used extensively in a wide range of printed electronics because of their widespread availability, electrical conductivity and low cost. Overcoming the inherent tendency of the nano-carbon to agglomerate to form a stable dispersion is necessary if these inks are to be taken from the lab scale to industrial production. Plasma functionalization of graphite nanoplatelets (GNP) adds functional groups to their surface to improve their interaction with the polymer resin. This offers an attractive method to overcome these problems when creating next generation inks. Both dynamic and oscillatory rheology were used to evaluate the stability of inks made with different loadings of functionalized and unfunctionalized GNP in a thin resin, typical of a production ink. The rheology and the printability tests showed the same level of dispersion and electrical performance had been achieved with both functionalized and unfunctionalized GNPs. The unfunctionalized GNPs agglomerate to form larger, lower aspect particles, reducing interparticle interactions and particle–medium interactions. Over a 12-week period, the viscosity, shear thinning behavior and viscoelastic properties of the unfunctionalized GNP inks fell, with decreases in viscosity at 1.17 s−1 of 24, 30, 39% for the ϕ = 0.071, 0.098, 0.127 GNP suspensions, respectively. However, the rheological properties of the functionalized GNP suspensions remained stable as the GNPs interacted better with the polymer in the resin to create a steric barrier which prevented the GNPs from approaching close enough for van der Waals forces to be effective

Stretchable Carbon and Silver Inks for Wearable Applications

For wearable electronic devices to be fully integrated into garments, without restricting or impeding movement, requires flexible and stretchable inks and coatings, which must have consistent performance and recover from mechanical strain. Combining Carbon Black (CB) and ammonia plasma functionalized Graphite Nanoplatelets (GNPs) in a Thermoplastic Polyurethane (TPU) resin created a conductive ink that could stretch to substrate failure (>300% nominal strain) and cyclic strains of up to 100% while maintaining an electrical network. This highly stretchable, conductive screen-printable ink was developed using relatively low-cost carbon materials and scalable processes making it a candidate for future wearable developments. The electromechanical performance of the carbon ink for wearable technology is compared to a screen-printable silver as a control. After initial plastic deformation and the alignment of the nano carbons in the matrix, the electrical performance was consistent under cycling to 100% nominal strain. Although the GNP flakes are pulled further apart a consistent, but less conductive path remains through the CB/TPU matrix. In contrast to the nano carbon ink, a more conductive ink made using silver flakes lost conductivity at 166% nominal strain falling short of the substrate failure strain. This was attributed to the failure of direct contact between the silver flakes

Printed Nanocarbon Heaters for Stretchable Sport and Leisure Garments

The ability to maintain body temperature has been shown to bring about improvementsin sporting performance. However, current solutions are limited with regards to flexibility, heatinguniformity and robustness. An innovative screen-printed Nanocarbon heater is demonstrated whichis robust to bending, folding, tensile extensions of up to 20% and machine washing. This combinationof ink and substrate enables the heated garments to safely flex without impeding the wearer. It iscapable of producing uniform heating over a 15 × 4 cm area using a conductive ink based on a blendof Graphite Nanoplatelets and Carbon Black. This can be attributed to the low roughness of theconductive carbon coating, the uniform distribution and good interconnection of the carbon particles.The heaters have a low thermal inertia, producing a rapid temperature response at low voltages,reaching equilibrium temperatures within 120 s of being switched on. The heaters reached the 40 ◦Crequired for wearable heating applications within 20 s at 12 Volts. Screen printing was demonstratedto be an effective method of controlling the printed layer thickness with good interlayer adhesionand contact for multiple printed layers. This can be used to regulate their electrical properties andhence adjust the heater performance

Atrium defines form

Includes abstract.Includes bibliographical references.The natural environment is deteriorating and electricity demand is outstripping supply partly due to our growing built environment and economy. In response there is a need for energy efficient office space to accommodate economic growth and help with the conservation of the environment. The inner city is a perfect location to achieve this using already deteriorated land and increasing the inner city density to reduce urban sprawl. There is an urgent need for developers to invest into the idea of energy efficiency however this has been restricted because of our economic environment and the need for just usable space. The creation of energy efficient buildings is typically more expensive mainly due to the introduction of new technologies and materials