Effect of curing conditions and harvesting stage of maturity on Ethiopian onion bulb drying properties

The study was conducted to investigate the impact of curing conditions and harvesting stageson the drying quality of onion bulbs. The onion bulbs (Bombay Red cultivar) were harvested at three harvesting stages (early, optimum, and late maturity) and cured at three different temperatures (30, 40 and 50 oC) and relative humidity (30, 50 and 70%). The results revealed that curing temperature, RH, and maturity stage had significant effects on all measuredattributesexcept total soluble solids

Evolving fracture patterns: columnar joints, mud cracks, and polygonal terrain

When cracks form in a thin contracting layer, they sequentially break the layer into smaller and smaller pieces. A rectilinear crack pattern encodes information about the order of crack formation, as later cracks tend to intersect with earlier cracks at right angles. In a hexagonal pattern, in contrast, the angles between all cracks at a vertex are near 120$^\circ$. However, hexagonal crack patterns are typically only seen when a crack network opens and heals repeatedly, in a thin layer, or advances by many intermittent steps into a thick layer. Here it is shown how both types of pattern can arise from identical forces, and how a rectilinear crack pattern evolves towards a hexagonal one. Such an evolution is expected when cracks undergo many opening cycles, where the cracks in any cycle are guided by the positions of cracks in the previous cycle, but when they can slightly vary their position, and order of opening. The general features of this evolution are outlined, and compared to a review of the specific patterns of contraction cracks in dried mud, polygonal terrain, columnar joints, and eroding gypsum-sand cementsComment: 19 pages, 9 figures, accepted for publication in Phil. Trans. R. Soc. A; theme issue on Geophysical Pattern Formation (to appear 2013

Kinetic roughening of a soft dewetting line under quenched disorder - a numerical study

A molecular-dynamics type simulation method, which is suitable for investigating the dewetting dynamics of thin and viscous liquid layers, is discussed. The efficiency of the method is exemplified by studying a two-parameter depinning-like model defined on inhomogeneous solid surfaces. The morphology and the statistical properties of the contact line is mapped in the relevant parameter space, and as a result critical behavior in the vicinity of the depinning transition is revealed. The model allows for the tearing of the layer, which leads to a new propagation regime resulting in non-trivial collective behavior. The large deformations observed for the interface is a result of the interplay between the substrate inhomogeneities and the capillary forces.Comment: 12 pages, 10 figure

The effect of soil moisture content on leaf extension rate and yield of perennial ryegrass

peer-reviewedThree experiments are described that were designed to evaluate the relationship between soil moisture and perennial ryegrass growth and leaf extension rate (LER) in loam or silt clay loam soil. When soil moisture was maintained at a range of proportions (0.5, 0.75, 1.0, 1.25) of field capacity (FC) in a pot experiment in a glasshouse, 0.75FC had consistently higher growth and LER than 0.5FC and, to a lesser extent, 1.25FC. The quadratic relationship between herbage growth and amount of water applied to maintain target field capacity, was stronger than for that between LER and the amount of water applied, with a maximum response at an application of about 2.5 L/m2 per day. In a microsward (soil depth of 30 cm in boxes 56 cm × 72 cm) trial inducing drought by withholding water for a range of durations resulted in a progressive decline in LER. When soil moisture content fell to about 0.4 of that of the consistently watered control LER was less than 0.1 of the control. However within one week of receiving water, even in the relatively severe drought treatment, LER was not significantly lower than the control treatment. LER was quadratically related to soil moisture content when soil was drying or after rewatering. In a further experiment on the microswards, reducing soil moisture content to about 0.18 g/g by limiting water in May-June resulted in a severe reduction in LER and growth rate and a decline in tillering rate. However, after application of the equivalent of 3 mm precipitation per day in late June, while soil moisture content remained relatively low (about 0.2 to 0.25 g/g soil), LER and herbage growth increased rapidly to as high as in consistently watered microswards. In a treatment in which soil moisture content eventually exceeded FC, LER and herbage growth declined with increase in excess above FC, concurring with findings in the steady state soil moisture experiment. Implications of the data for prediction of production from sown grass swards using temperate maritime grass-growth models are that: (1) during drought, when rainfall resumes, regrowth will be influenced more by amount of rainfallthan soil moisture content and (2) excess soil moisture should be taken into account, including effects of reduced nutrient uptake and post-anoxia stress

Resource and non-resource root competition among trees of different successional status

1. This study assessed the effects of resource (i.e. nutrients) and non-resource (i.e. interference for space) competition from fine roots of competing grasses on the growth, morphology and architecture of fine roots of four tree species of varying successional status: Populus deltoides × P. balsamifera (a\ud hybrid), Betula papyrifera, Acer saccharum and Fraxinus americana. We tested the general hypothesis that tree fine-roots are affected by both below-ground resource and non-resource competition from non-self plants, and the more specific hypothesis that this effect is stronger in early- successional tree species.\ud 2. The experiment was conducted in split-containers where half of the roots of tree seedlings experienced either below-ground resource competition or non-resource competition, or both, by grasses while the other half experienced no competition.\ud 3. The late-successional tree species A. saccharum and\ud F. americana were mostly affected by resource competition, whereas the early-successional P. deltoides × balsamifera\ud and B. papyrifera were strongly affected by both resource and non-resource competition. Non-resource competition reduced fine-root growth, root branching over root length (a measure of root architecture) and specific root length (a measure of root morphology) of both early-successional species.\ud 4. Synthesis. This study suggests that early-successional tree species have been selected for root avoidance or segregation and late-successional tree species for root tolerance of competition as mechanisms to improve below-ground resource uptake in their particular environments. It also\ud contradicts recent studies showing perennial and annual grasses tend to overproduce roots in the presence of non-self conspecific plants. Woody plants, required to grow and develop for long periods in the presence of other plants, may react differently to non-self root competition than perennial or\ud annual grasses that have much shorter lives

On the design of an interactive biosphere for the GLAS general circulation model

Improving the realism and accuracy of the GLAS general circulation model (by adding an interactive biosphere that will simulate the transfers of latent and sensible heat from land surface to atmosphere as functions of the atmospheric conditions and the morphology and physiology of the vegetation) is proposed

Passive Hydro-actuated Unfolding of Ice Plant Seed Capsules as a Concept Generator for Autonomously Deforming Devices

In der Natur und ihren biologischen Systemen existieren zahlreiche Beispiele für gerichtete Bewegung durch spezifische Reaktion auf externe Stimuli. Diese potentiellen Quellen der Inspiration dienen oft als Vorbilder für energieeffiziente "Smart" Technologien. Vom Wasser getriebenen schnellen Zuschnappen der Venusfliegenfalle bis zum einfacheren ebenso hydroresponsiven Biegen der Weizengrannen, viele Pflanzen haben im Laufe der Evolution verschiedene Mechanismen entwickelt, um Wasser als Triebkraft ihrer Aktoren-Gewebe zu nutzen, die für spezifische und gerichtete Bewegung sowie die gewünschte Verformung sorgen. Das ist diesen Pflanzen möglich durch die Organisation ihrer Gewebe in ausgereiften, komplexen und hierarchisch organisierten Architekturen auf verschiedensten Skalen. Einige Arten der Familie Aizoaceae, auch bekannt als Mittagsblumen oder Ice plant, zeigen ein geniales Beispiel für solche passiven Betätigungssysteme, da sie einen "intelligenten" Mechanismus entwickelt haben, um ihre Schutzsamenkapseln öffnen zu lassen und die Samen nur in Anwesenheit von flüssigem Wasser (Regen) freizugeben. Schwerpunkt der ersten Phase dieser Arbeit war die Untersuchung der zu Grunde liegenden Mechanismen und der strukturellen und kompositorischen Basis von Wasser-getriebenen Bewegungen der Samenkapseln von Ice plant (Delosperma nakurense) auf ihren verschiedenen hierarchischen Ebenen. Fünf hygroskopische Kiele erwiesen sich als aktive "Muskeln", die zu einer reversiblen origamiartigen Entfaltung der Samenkapsel führen, wenn diese mit Wasser benetzt wird. Jeder Kiel besteht aus zwei wabenartigen Geweben, die aus hochgradig schwellfähigen und elliptisch-sechseckig geformten Zellen zusammengesetzt sind, die entlang einem inerten Träger organisiert sind. Als Hauptmotor der Aktuation wurde die signifikante Schwellung von hochgradig schwellfähigen zellulosereichen Innenschichten (CIL) im Lumen der Zellen identifiziert. Die Morphologie der CIL und deren physikochemische Reaktion auf Wasser wurde unter Verwendung einer Vielzahl von Techniken untersucht und damit gezeigt, dass der Entropiegewinn während der Wasserabsorption die Hauptantriebskraft für die Schwellung der Zellen ist. Die Umsetzung dieser relativ kleinen Energiebeiträge in eine konzertierte und komplexe makroskopische Bewegung, wurde durch ein optimiertes Design auf den verschiedenen Ebenen der hierarchischen Organisation des Systems erläutert. Das kooperative anisotropische Anschwellen der Zellen des hygroskopischen Gewebes führt durch das Timoschenko Doppelschicht-Biegeprinzip zu einer Umsetzung in eine Biegebewegung der Strukturen und letztlich zur Entfaltung der Samenkapseln. Inspiriert von den zugrunde liegenden Mechanismen in Ice plants, wurden zwei unterschiedliche Strategien entwickelt, um durch kleine Dehnungen im mikroskopischen Bereich eine vorprogrammierte Makro-Bewegung einer Wabenstruktur zu ermöglichen. Durch eine geschickte Anwendung dieses einfachen Prinzips, kann eine Mimik des biologischen Vorbilds im weiteren technischen Sinne zu zahlreichen Anwendungsbeispielen führen, wie als passive Schalter und Aktoren in der Biomedizin, Landschaftsgestaltung oder der Architektur.Numerous examples of actuated-movements with specific responses of the structure to external stimuli can be found in biological systems, which can be a potential source of inspiration for the design of energy-efficient "smart" devices. From the hydro-driven rapid snapping of the Venus fly trap leaves to simple hydro-responsive bending of wheat awns, various plants have evolved different mechanisms to utilize water as an actuator to undergo a desired deformation via sophisticated architecture at different hierarchical levels of their systems. Some species of the family Aizoaceae, also known as ice plants, show an ingenious example of such passive actuation systems, as they evolved a smart mechanism to open their protective seed capsules and release their seeds only in the presence of liquid water (rain). The scope of the first phase of the thesis was to investigate the underlying mechanism and the structural and compositional basis of the hydro-actuated movement of the ice plant seed capsules (Delosperma nakurense) at several hierarchical levels. Five hygroscopic keels were found to be the active muscles responsible for the reversible origami-like unfolding of the seed capsule upon wetting. Each keel consists of two honeycomb-like tissues made up of highly swellable hexagonal/elliptical shape cells running along an inert backing tissue. The significant swelling of a highly swellable cellulosic inner layer (CIL) inside the lumen of these cells was found to be the main engine of the actuation. The morphology and physicochemical response of the CIL to water was studied using a variety of techniques and it was shown that the entropic changes during water absorption were the main driving force for swelling of the cells. The translation of such relatively small available energy to the complex movement at a macro scale was explained by an optimized design at different hierarchical levels of the system. The cooperative anisotropic swelling of the cells in the hygroscopic tissue is translated into a flexing movement of the structure via simple Timoshenko’s bilayer bending principle, which then results in an unfolding of the seed capsules. Inspired by the underlying mechanism in ice plant, two different strategies were developed to translate small strains at micro scale into a pre-programmed macro movement of a honeycomb structure. Through a clever application of the same simple concepts, one can "mimic" the biological model system in a broader engineering sense, with potential applications of such passive switches in biomedicine, agricultural engineering or architectural design

Drying Agrochemical Droplets on Model Surfaces

This project addressed the mechanism of the action of surfactants, used as agrochemical adjuvants, and the physico-chemical interaction between adjuvants and a fungicide active ingredient (AI), on a model surface. The first part of the project studied the influence of surfaces with different wettabilities on the mode of evaporation for water droplets, as a reference, and then with different surfactant solutions at different concentrations with and without the addition of AI. In order to do that, a reproducible method to print droplets with the specific size for agrochemical applications was developed. The internal flows for different agrochemical solutions were studied to understand the transport of surfactants and particles within the droplets. Two main agrochemical formulations were used: an alkyl ethoxylate surfactant (Surf1) and an amidoamine-based surfactant (Surf2) both with the addition of a fungicide called Tebuconazole resulting in a suspension and an emulsion respectively. The properties of the bulk solutions were analysed by surface tensiometry and proton nuclear magnetic resonance (1H-NMR) to determine the ability of these surfactants to form micelles and solubilise a hydrophobic active ingredient (AI). Diffusion-ordered spectroscopy (DOSY) showed that only Surf1 formed micelles. There was no difference in the diffusion coefficient for Surf2 at any of the concentrations tested, from which it can be concluded that Surf2 does not form micelles. The evaporation of droplets made of different solutions gave different dried deposits on a substrate. Different strategies were developed to control the deposit structure in order to inhibit the coffee-ring effect (CRE): i) a sol-gel transition in a suspension of a nanoparticle clay (Laponite) and ii) silica particles; both added to the alkyl ethoxylate surfactant. The addition of Laponite and silica particles increased the surface tension of the final formulations at any of the concentrations. The purpose of these two strategies was to obtain more uniform deposits so that the amount of surfactant and AI were more equal along the deposit. However, Laponite formed uniform deposits because the contact line (CL) receded producing deposits of a smaller area and silica particles did not suppress the CRE. “Superspreaders” such as Silwet Gold, an vi organosilicone surfactant, and Capstone® FS30, a fluorosurfactant, were added to the amidoamine-based surfactant in order to lower the contact angle of the oil drops after drying to increase the contact between the agrochemical solution and the surface, and thus increase the efficacy. The contact angle of the small droplets inside the deposit was lower when Silwet Gold was added to Surf2 + AI at 0.03 wt%. The morphology of the dried deposit and the spatial distribution of the AI particles were analysed by scanning electron microscopy (SEM) and the chemical composition was analysed by energy dispersive X-ray spectroscopy (EDS) and Raman spectroscopy. A Raman imaging system was developed to improve the ability to map compounds on a surface. Raman imaging had the required sensitivity to confirm the co-localization of surfactant and AI molecules in the dried deposit. A quantitative method to achieve compositions by Raman spectroscopy was developed. The last part of the thesis consists of a study of the penetration of AI through the cuticle of Clivia Regel Minata in a Franz diffusion cell by two different methods: infinite dose system and simulation of foliar penetration (SOFP). Clivia is selected as a model plant as it does not have stomata that might affect the transport of AI1. The penetration of AI was improved by the addition of surfactant to the formulation. Surfactants below the CMC behaved very similarly to the surfactant-free formulations. Surfactants above CMC or above the solubility limit showed the highest penetration for the infinite dose experiments. In SOFP, the difference in AI penetration between the formulations were not significantly different. Franz cell diffusion is a useful method to study the trends for the penetration of AI through the cuticles of the leaves, however, the leaf-to-leaf variation is still too large to draw firm conclusions about foliar efficiency

Extreme mechanical resilience of self-assembled nanolabyrinthine materials

Low-density materials with tailorable properties have attracted attention for decades, yet stiff materials that can resiliently tolerate extreme forces and deformation while being manufactured at large scales have remained a rare find. Designs inspired by nature, such as hierarchical composites and atomic lattice-mimicking architectures, have achieved optimal combinations of mechanical properties but suffer from limited mechanical tunability, limited long-term stability, and low-throughput volumes that stem from limitations in additive manufacturing techniques. Based on natural self-assembly of polymeric emulsions via spinodal decomposition, here we demonstrate a concept for the scalable fabrication of nonperiodic, shell-based ceramic materials with ultralow densities, possessing features on the order of tens of nanometers and sample volumes on the order of cubic centimeters. Guided by simulations of separation processes, we numerically show that the curvature of self-assembled shells can produce close to optimal stiffness scaling with density, and we experimentally demonstrate that a carefully chosen combination of topology, geometry, and base material results in superior mechanical resilience in the architected product. Our approach provides a pathway to harnessing self-assembly methods in the design and scalable fabrication of beyond-periodic and nonbeam-based nano-architected materials with simultaneous directional tunability, high stiffness, and unsurpassed recoverability with marginal deterioration