Combining Scenario Workshops and Participatory System Dynamics Modelling to Study Food Security. A case study with farmers in Zambia

Food security, which affects mainly developing countries, is a worldwide problem that has called the attention of the economic, political and scientific community. Achieving food security is a very complex process that involves not only the ability of farming but also a constant adaptation to natural phenomena, as for example, rainfall patterns. Limited knowledge and access to information and technologies, restrict the capacity of local farming communities to achieve food security. Furthermore, there is a lack of suitable methods and tools for involving stakeholders, such as farmers, in the development and assessment of food policies and their long-term system-wide effects. The main goal of this research is to investigate how the use of mixed-methods – scenarios and participatory System Dynamics (SD) modelling – are capable of improving understanding and an integrative view of food systems, serving as a lever for supporting food security decision-making processes. Additionally, this research aims to answer the following two questions: i) How can scenarios and participatory SD be used together to study plausible futures of food security involving smallholder farmers in developing countries?; ii) What are the possible policy pathways to avoid undesirable situations and to stimulate desirable ones, in a context of subsidence farming in Sub-Saharan African countries?. For this specific purpose, a group of smallholder farmers in Zambia was analyzed as a case study. First, a workshop was implemented in which a scenario of poor rainfall and no government help was developed. In order to achieve food security, participants had to find policy proposals and pathways to avoid or to overcome this undesired scenario. Subsequently, from the scenario workshop data, causal loop diagrams (CLD) were built using a systematic coding process. The next steps were to analyse policy proposals through a cross-impact analysis and develop an outline of pathways to study the complementarity and compatibility of such proposals. The 11 policy proposals were Charcoal Business; Livestock Business; Groundnuts Business; Gardening; Loan; Piecework; Land (productive land); Rental Business; Partnership; Legislation for Deforestation/Afforestation; and, Retention Basins/Drilling Boreholes. Finally, it was possible to design an innovative Action Plan that shows the pathways and the pace at which each proposal may achieve food security. It was concluded that scenario workshop and participatory SD may tightly coupled since these methods complement each other, stimulating system thinking and co-creation of knowledge. Scenario workshops are a disruptive and exploratory method, as it allows to elicit creative and plausible images from participants. Participatory SD supports decision-making processes by analysing policy proposals and its pathways, leading to the elaboration of joint action plans. In the Zambian case, from the 11 plausible policy proposals, it was found that Piecework enables a swifter path to achieve food security, while Rental Business would be the slowest. Additionally, it was found that some of the policy proposals could be reinforced if implemented together, while others, such as Charcoal Business and Legislation for Deforestation/Afforestation, did not show such potential. A follow-up survey with workshop participants showed that they were following the Action Plan, confirming the preference for the short-term policy proposal pathways

Untersuchungen zur thermionischen Erzeugung von Alkali-Ionenstrahlen

Gegenstand dieser Arbeit sind Studien zur thermionischen Erzeugung von Alkali-Ionen. Ausgangspunkt waren dabei die in der Arbeitsgruppe Weitzel existierenden Alkali-IonenEmitter auf Basis von MAlSi2O6 mit M = K, Rb, Cs. Diese Emitter basieren auf der Einbettung des Emittermaterials MAlSi2O6 in einer Metallmatrix und sind in der Lage, einen hochreinen Ionenstrahl mit einer Stromstärke im Bereich von etwa 100 nA zu erzeugen. Im Verlauf dieser Arbeit zeigte sich, dass es mit diesem Aufbau nicht möglich ist, Lithium- und Natrium-Ionen aus MAlSi2O6 mit M = Li, Na zu erzeugen und sich die erhaltenen Kenngrößen für die Emission, wie beispielsweise die Austrittsarbeit, deutlich von Probe zu Probe unterscheiden. Als Alternative wurden sogenannte Filament-Emitter, bei denen eine Metallfolie als Widerstandsheizung und Probenträger eingesetzt wird, durch Aufschmelzen des reinen Emittermaterials auf das Filament hergestellt. Dabei wurde auf den Zusatz eines Matrixmetalls verzichtet. Mit der Verwendung von Emittermaterialien der Zusammensetzungen MAlSiO4 und MalSi2O6 mit M = Li, Na, K, Rb, Cs war es möglich, Lithium-, Natrium-, Kalium-, Rubidium- und Cäsium-Ionenstrahlen zu erzeugen. Weiterhin eröffneten systematische Studien der Temperatur- und Feldabhängigkeit der Emission den Zugang zu Kenngrößen der thermionischen Emission. Die Austrittsarbeit zeigt beispielsweise eine deutliche Abhängigkeit von der Struktur der Emittermaterialien. Der Einfluss des anionischen Gitters wurde durch Einsatz von CsMSi2O6 und CsMGe2O6 mit M = B, Al, Ga, F e als Emittermaterial untersucht. Für die Feldabhängigkeit wurde für alle untersuchten Emittermaterialien der Übergang von der raumladungsbegrenzten zur feldverstärkten Emission beobachtet. Die Analyse der kinetischen Energie der erzeugten Ionenstrahlen wurde durch Bremsfeldmessungen realisiert. Die erhaltenen Ergebnisse für LiAlSi2O6 sind in guter Übereinstimmung mit numerischen Simulationen des Emissionsverhaltens. Zum Abschluss der Arbeit wurde die thermionische Emission erstmals als Zugangsweg zur Bestimmung der ionischen Austrittsarbeit für Lithium aus Lithium-Cobalt-Oxid genutzt. Die so erhaltene ionische Austrittsarbeit von etwa 4 eV ist in sehr guter Übereinstimmung mit einem aus theoretischen Überlegungen abgeleiteten Wert von 3.6 − 4.5 eV

Temperature-dependent rate coefficients for the reactions of the hydroxyl radical with the atmospheric biogenics isoprene, alpha-pinene and delta-3-carene

Pulsed laser methods for OH generation and detection were used to study atmospheric degradation reactions for three important biogenic gases: OHCisoprene (Reaction R1), OH+α-pinene (Reaction R2) and OH+Δ- 3-carene (Reaction R3). Gas-phase rate coefficients were characterized by non-Arrhenius kinetics for all three reactions. For (R1), k1 (241-356 K)= (1:93±0:08)× 10-11 exp{(466±12)/T} cm3 molecule-1 s-1 was determined, with a room temperature value of k1 (297 K)= (9:3± 0:4)×10-11 cm3 molecule-1 s-1, independent of bath-gas pressure (5-200 Torr) and composition (MDN2 or air). Accuracy and precision were enhanced by online optical monitoring of isoprene, with absolute concentrations obtained via an absorption cross section, αisoprene = (1:28±0:06)× 10-17 cm2 molecule-1 at λ = 184:95 nm, determined in this work. These results indicate that significant discrepancies between previous absolute and relative-rate determinations of k1 result in part from σ values used to derive the isoprene concentration in high-precision absolute determinations. Similar methods were used to determine rate coefficients (in 10-11 cm3 molecule-1 s-1/ for (R2)-(R3): k2 (238-357 K)= (1:83±0:04) ×exp{(330±6)/T } and k3 (235-357 K)= (2:48±0:14) ×exp{(357±17)/T }. This is the first temperature-dependent dataset for (R3) and enables the calculation of reliable atmospheric lifetimes with respect to OH removal for e.g. boreal forest springtime conditions. Room temperature values of k2 (296 K)= (5:4±0:2) ×10-11 cm3 molecule-1 s-1 and k3 (297 K)= (8:1±0:3)×10-11 cm3 molecule-1 s-1 were independent of bathgas pressure (7-200 Torr, N2 or air) and in good agreement with previously reported values. In the course of this work, 184.95 nm absorption cross sections were determined: σ = (1:54±0:08) ×10-17 cm2 molecule-1 for α-pinene and (2:40±0:12)×10-17 cm2 molecule-1 for 1-3-carene

Gingival tissue attachment and blood responses to nanoporous bioactive coatings on zirconia

Zirconia implant abutments have gained popularity over the past few years as a substitute for the traditionally used titanium alloy abutments. However, research on the soft-tissue responses of zirconia and improving the zirconia surface properties towards immediate soft-tissue integration are limited. This series of in vitro studies aimed at evaluating tissue and cellular responses of commercially available zirconia versus zirconia provided with sol-gel derived TiO2 coating. Final purpose of the research project was to optimize zirconia surface properties for fabrication of implant abutments, which enhances gingival tissue attachment. Coatings were prepared from tetraisopropyl orthotitanate solution by dip-coating method. The effect of coatings and the coating process on the mechanical properties of zirconia was evaluated by biaxialflexural strength test. Human gingival epithelial and fibroblast cell responses – adhesion kinetics, adhesion strength, and proliferation– was studied in cell culture environment. Blood response, including blood clotting ability, protein adsorption and platelet adhesion and morphology was evaluated. A novel tissue culture method, developed earlier by the research group, was used to evaluate porcine gingivaltissue attachment on the coated and non-coated zirconia implants. Adhesion was evaluated using routine microscopy coupled with immunohistochemical staining. Furthermore, the strength of bond between tissue and implants was analyzed utilizing dynamic mechanical analysis. The biaxial flexural strength of zirconia specimens was unaffected by the coating process. Significant differences were observed in blood coagulation between the coated and non-coated zirconia surfaces. UV treatment of the TiO2 coated specimens enhanced blood coagulation. Blood platelets also appeared at a higher activation state on coated specimens although no differences in protein adsorption were observed. TiO2 coated zirconia were significantly more hydrophilic with higher total surface free energy than non-coated ones. Cell proliferation and adhesion was significantly higher on coated specimens. Microscopic observation of gingival tissue attachment on coated implants identified laminin-g-2 at the attachment of epithelium to implant indicating direct attachment. This observation was absent in noncoated zirconia controls. Furthermore, gingival tissue attachment to coated zirconia implants demonstrated higher dynamic modulus of elasticity and higher creep modulus. Sol-gel derived TiO2 coatings on zirconia enhance trombogenicity and facilitate direct gingival tissue attachment on zirconia surface. These findings indicate that TiO2 coating on zirconia abutments has good potential to improve implant treatment results

Synthesis, Characterisation, and MD Investigation of the Mechanical and Catalytic Properties of Ceria Nanocubes and Ceria-Aerogel Nanocomposites

Nanoceria has become a widely used component in catalysis due to its unprecedented ability for oxidation/reduction. Irreversible deformation however plagues the operation of these materials, extinguishing their catalytic properties, and therefore they need protecting from harsh operating conditions. Furthermore, particle agglomeration can cause loss of catalytic activity. Here, two solutions to protecting nanoceria are presented, utilising both experiment analysis and atomistic molecular dynamic (MD) modelling. In particular how the use of sacrificial materials can protect a ceria nanocube, allowing stress of 40 GPa, in comparison to 2.5 GPa unprotected, before plastic deformation occurs, and how encapsulating ceria nanocubes in an aerogel matrix can prevent aggregation, retaining catalytic activity, and also act as a sacrificial material to prevent mechanical wear. A ceria nanocube synthesis was optimised and Lanthanum introduced as a dopant with the aim of improving the catalytic activity of the ceria nanocubes by promoting the formation of oxygen vacancies (Chapter 3). The resulting nanoparticles were encapsulated in an aerogel host matrix, forming nanocomposites, with the aim of preventing aggregation. L3 edge HERFD-XANES was used to investigate the oxidation/reduction ability of the ceria nanocubes and nanocomposites under different operating temperatures (Chapter 4). This presented improved catalytic performance in ceria nanoparticles dispersed in an aerogel matrix, with further improvement indicated with the presence of a La-dopant. An amorphisation-recrystallisation technique was employed for the atomistic MD investigation of sacrificial barriers (Chapter 5), which was further developed to include temperature variations, compression rate, and a calculated dynamic surface area (Chapter 6). This demonstrated that sacrificial barriers can allow for higher applied stress in a system before plastic deformation occurs, preserving the structural integrity. Dynamic surface area calculations presented stress-strain data in high concordance with experiment, whereas increased system temperature presented a reduction of measured stress, and compression rate variation presented further clarity of individual deformation events. Furthermore, a new technique for the MD simulation of SiO2 aerogel was developed (Chapter 7), where a seed and cluster growth method was employed to form the aerogel, then uniaxial force was applied to investigate the resulting mechanical properties

Simulación de imágenes de microscopía de barrido por efecto túnel (STM) de moléculas orgánicas adsorbidas en superficies metálicas

En el presente trabajo de investigación doctoral se han simulado las imágenes de microscopía de barrido por efecto túnel (STM) de la molécula dianhídrido 3,4,9,10 perilen-tetracarboxílico (DAPTC) adsorbida en la superficie metálica Au(111) limpia y modificada con yodo (fases Au(111)-(÷3x÷3)R30°-I y Au(111)- c(px÷3-R30°)-I), utilizando la aproximación de Tersoff y Hamann. Los cálculos de la estructura electrónica del sistema de adsorción, así como del adsorbato y los substratos aislados, fueron efectuados con la Teoría de Funcionales de la Densidad en la Aproximación de Densidad Local (DFT-LDA) utilizando pseudopotenciales y bases de ondas planas. Las diversas imágenes de STM simuladas para el adsorbato, los substratos y los sistemas de adsorción son analizadas, indicando el efecto que sobre ellas tiene la diferencia de potencial punta-muestra, el valor de isosuperficie de la densidad local de estados integrada y la temperatura. Se encontró también que el grado de perturbación del espectro de densidad de estados desocupados del sistema de adsorción y el grado de ruptura de la simetría inducido por el substrato en las correspondientes imágenes de STM simuladas, permiten realizar una estimación cualitativa de la energía de interacción adsorbato-superficie. En este contexto el proceso de adsorción de la molécula DAPTC en las superficie Au(111) limpia fue caracterizado como una quimisorción débil, mientras que la adsorción sobre las superficies Au(111)- (÷3x÷3)R30°-I y Au(111)-c(px÷3-R30°)-I fueron considerados procesos de fisisorción. En imágenes de STM simuladas para estados desocupados de DAPTC adsorbido en las superficies metálicas modificadas con yodo, en condiciones de bajo voltaje y valores intermedios para la isosuperficie de la densidad local de estados integrada, se manifiesta el fenómeno de transparencia atómica

Histomorphometric and Biomechanical Analyses of Osseointegration of Four Different Orthodontic Mini Implant Surfaces

Indiana University-Purdue University Indianapolis (IUPUI)Objective: To evaluate the osseointegration potential of four different surfaces of mini-implants .We hypothesized that mini-implants surface roughness alters the intrinsic biomechanical properties of the bone integrated to titanium. Materials and Methods: Mini implants and circular discs were made from alloy Ti6Al4V grade 5. On the basis of surface treatment study was divided into 4 groups: Group 1: Machined: no surface treatment, Group 2: Acid etched: with hydrochloric acid, Group 3: Grit Blasted with alumina and Group 4: Grit blasted +Acid etched. Surface roughness parameters (mean surface roughness: Ra and Quadratic Average roughness: Rq) of the four discs from each group were measured by the optical profilometer. Contact angle measurement of 3 discs from each group was done with a Goniometer. Contact angle of liquids with different hydrophobicity and hydrophilicity were measured. 128 mini implants, differing in surface treatment, were placed into the tibias and femurs of 8 adult male New Zealand white rabbits. Biomechanical properties (Removal torque and hardness) measurements and histomorphometric observations were measured. Results: Ra and Rq of groups were: Machined (1.17±0.11, 2.59±0.09) Acid etched (1.82±0.04, 3.17±0.13), Grit blasted (4.83±0.23, 7.04±0.08), Grit blasted + Acid etched (3.64±0.03, 4.95±0.04) respectively. Group 4 had significantly (p=0.000) lower Ra and Rq than Group 3. The interaction between the groups and liquid was significant. Group 4 had significantly lower contact angle measurements (40.4°, 26.9°), both for blood and NaCl when compared to other three groups (p≤0.01). Group 4 had significantly higher torque than Group 3 (Tibia: 13.67>9.07N-cm; Femur: 18.21>14.12N-cm), Group 4 (Tibia: 13.67>9.78N-cm; Femur: 18.21>12.87N-cm), and machined (Tibia: 13.67>4.08N-cm; Femur: 18.21>6.49N-cm). SEM analysis reveals significantly more bone implant gap in machined implant surfaces than treated implant surfaces. Bone to implant contact had significantly higher values for treated mini implant surface than machined surface. Hardness of the bone near the implant bone interface is 20 to 25% less hard than bone 1mm away from it in both Femur and Tibia. Conclusion: Surface roughness and wettability of mini implants influences their biological response. Grit blasted and acid etched mini implants had lowest contact angle for different liquids tested and highest removal torques