Magnetisation reversal mechanism in Co-Cr media for perpendicular magnetic recording

In this study Co---Cr thin films with perpendicular anisotropy are investigated. Three films with values for Hc of 11, 90 and 170 kA/m have been selected for this paper. Besides the coercivily several other parameters such as the Hc/Hk, Cr-segregation, domain structure, column sizes, etc. were studied by VSM, SEM, NMR, MFM, AFM and selective etching. The anomalous Hall effect (AHE) has been used to record the hysteresis curves of submicron Hall crosses. This very sensitive technique in combination with e-beam lithography and ion-beam etching resulted in the recording of AHE hysteresis loops with dimensions of the Hall crosses as small as 0.3 × 0.3 ¿m2. The AHE loops of three samples, with less than 60 columns, show different micromagnetic properties. Only the sample with Hc1 = 90 kA/m shows clear steps in the curves above the noise level. The largest steps correspond with the reversal of one column and the total number of steps was five times the number of columns for this sample. The different reversal mechanisms observed by the AHE are related to the differences in structure, coercivity and domain size

Real-Time Water Vapor Maps from a GPS Surface Network: Construction, Validation, and Applications

In this paper the construction of real-time integrated water vapor (IWV) maps from a surface network of global positioning system (GPS) receivers is presented. The IWV maps are constructed using a twodimensional variational technique with a persistence background that is 15 min old. The background error covariances are determined using a novel two-step method, which is based on the Hollingsworth¿Lonnberg method. The quality of these maps is assessed by comparison with radiosonde observations and IWV maps from a numerical weather prediction (NWP) model. The analyzed GPS IWV maps have no bias against radiosonde observations and a small bias against NWP analysis and forecasts up to 9 h. The standard deviation with radiosonde observations is around 2 kg m-2, and the standard deviation with NWP increases with increasing forecast length (from 2 kg m-2 for the NWP analysis to 4 kg m-2 for a forecast length of 48 h). To illustrate the additional value of these real-time products for nowcasting, three thunderstorm cases are discussed. The constructed GPS IWV maps are combined with data from the weather radar, a lightning detection network, and surface wind observations. All cases show that the location of developing thunderstorms can be identified 2 h prior to initiation in the convergence of moist air

Pension fund finance and sponsoring companies: Empirical evidence on theoretical hypotheses

This study presents empirical evidence on the influence of sponsoring companies on the funding and portfolio allocation of pension funds, an issue on which most extant literature is theoretical. We use a unique microdataset of 550 Dutch defined benefit company pension funds and 100 sponsoring firms over 1996-2005 to test the relevance of the main theoretical hypotheses, the first paper to do so in a comprehensive manner. We find that pension funds have lower cover ratios when (1) their sponsoring company is highly leveraged, (2) the fund’s return on assets is relatively low, and (3) the sponsoring firm is small. Further, defined benefit pension funds are found to invest more in shares when their sponsoring companies are highly leveraged. These links in general suggest higher risk in the sponsor leads to correspondingly higher risk in the fund, and warrant close attention by regulators

Risk stratification for ventricular arrhythmias in ischemic cardiomyopathy::the role of non-invasive cardiac imaging

Rossum, A.C. van [Promotor]Allaart, C.P. [Copromotor]Knaapen, P. [Copromotor

Asset Price Shocks, Real Expenditures, and Financial Structure: A Multi-Country Analysis

This paper examines the responses of private consumption, residential investment, and business investment in 11 EU countries, Japan, and the United States to shocks in housing and equity prices. The effects are assessed with a Structural Vector Auto Regressive (SVAR) model, and four key findings emerge. First, the impacts of asset price shocks are heterogeneous across countries. Second, these heterogeneous responses are systematically related to cross-country variation in financial structure. We are thus able to document the importance of a wealth/balance sheet channel for private consumption and residential investment and an equity finance channel for business investment. Third, for a given country, housing shocks have a much greater impact than equity shocks. Fourth, variance decompositions indicate that monetary policy reacts to equity price shocks but not to housing price shocks. These results highlight the important role played by asset prices on real activity and fuel the debate about the inclusion of asset prices in the formulation of monetary policy.monetary policy, asset prices, structural VAR

Asset Price Shocks, Real Expenditures, and Financial Structure:A Multi-Country Analysis

This paper examines the response of the economies of 11 EU countries, Japan, and the United States to shocks in housing and equity prices. The effects are assessed with a Structural Vector Auto Regressive (SVAR) model, and four key findings emerge. First, the impacts of asset price shocks are heterogeneous across countries. Second, these heterogeneous responses are systematically related to cross-country variation in financial structure, and we are thus able to document the importance of a wealth/balance sheet channel for consumption and an equity finance channel for investment. Third, for a given country, housing shocks have a much greater impact than equity shocks. Fourth, variance decompositions indicate that monetary policy reacts to equity price shocks but not to housing price shocks. These results highlight the important role played by asset prices on real activity, and fuel the debate about the inclusion of asset prices in the formulation of monetary policy.

The asymptotic regimes of tilted Bianchi II cosmologies

In this paper we give, for the first time, a complete description of the dynamics of tilted spatially homogeneous cosmologies of Bianchi type II. The source is assumed to be a perfect fluid with equation of state $p = (\gamma -1) \mu$, where $\gamma$ is a constant. We show that unless the perfect fluid is stiff, the tilt destabilizes the Kasner solutions, leading to a Mixmaster-like initial singularity, with the tilt being dynamically significant. At late times the tilt becomes dynamically negligible unless the equation of state parameter satisfies $\gamma > {10/7}$. We also find that the tilt does not destabilize the flat FL model, with the result that the presence of tilt increases the likelihood of intermediate isotropization

Potato diversity at height: multiple dimensions of farmer-driven in-situ conservation in the Andes

In-situ conservation Two types of in-situ conservation of crop genetic resources can be distinguished: farmer-driven and externally driven. The first is subject of this thesis and refers to the persistence of potato genetic resources in areas where everyday practices of farmers maintain diversity on-farm. The second concerns the more recent phenomenon of Research & Development (R&D) interventions which aim to support in-situ conservation by farmers. In this study, farmer-driven in-situ conservation of the potato in the central Andes of Peru is investigated at different system levels from alleles, cultivars, and botanical species up to the level of the landscape, as well as the interconnected seed and food systems. Dimensions of time and space are inferred upon by taking both annual and longer-term spatial patterns into account. Further, diversity is linked to selected farmer-based and external drivers. Objective and study area The overall objective of the study is to enhance our understanding of farmer-driven in-situ conservation and the context in which it takes place. The main field research was conducted between 2003 and 2006 in eight farmer communities following a north-south transect through the department of Huancavelica. Communities were selected on the basis of distribution and distance along the north-south transect, tradition of potato cultivation, ethnicity, and relative distance from major markets or cities. Depending on the specific dimension of farmer-driven in-situ conservation investigated, a range of different methods and tools were used. Chapter 1 provides a brief description of the study area and an overview of the research methods used. Species, cultivar and allelic diversity In chapter 2 the species, morphological and molecular diversity of Andean potatoes in Huancavelica is treated at different scales of conservation: farmer family, community, geographically distanced, regional, in-situ and ex-situ subpopulations. The infraspecific diversity of in-situ collections was characterized using morphological descriptor lists and 18 polymorphic microsatellite markers (SSR). Botanical species were determined through ploidy counts in combination with morphological keys. Datasets were used for descriptive statistics, (dis)similarity analysis, dendrogram construction, cophenetic analysis, matrix correlations calculations (Mantel tests), and Analysis of Molecular Variance (AMOVA). Results show that farmers in Huancavelica maintain high levels of species, morphological and molecular diversity. All cultivated potato species with the exception of Solanum phureja and Solanum ajanhuiri proved to be present. Tetraploid species were most abundant followed by diploids, triploids and pentaploids. A total of 557 morphologically unique cultivars were identified based on the morphological characterization of 2,481 accessions belonging to 38 in-situ collections. Genetic fingerprinting of 989 accessions belonging to 8 in-situ collections resulted in the identification of 406 genetically unique cultivars. AMOVA shows that the principal source of molecular variation is found within rather than between geographically distanced and farmer family subpopulations. No evidence of genetic erosion was found as the contemporary regional in-situ population and a geographically restricted subset of CIP´s ex-situ core collection share 98.8% of allelic diversity. Yet, in-situ collections contain numerous unique genotypes. Indigenous biosystematics The indigenous biosystematics of potatoes (folk taxonomy, folk descriptors and nomenclature) is investigated in chapter 3. The chapter includes an extensive literature review on the subject. Folk taxonomy was investigated with the use of grouping exercises with farmers, participant observation, and comparison of farmer-recognized groups with formal classification based on morphological descriptors and 18 polymorphic microsatellite markers (SSR). Analysis of the latter was based on (dis)similarity analysis, dendrogram construction and consequent levels of coherent clustering by folk taxonomic entity (folk specific and varietal taxon). Ethnobotanical free and indicated listing exercises with farmers were used for research concerning folk descriptors. Descriptive statistics were used for analysis and interpretation. Nomenclature was investigated by applying nomenclature surveys, participant observation and basic ethnolinguistic analysis of regional names. Folk taxonomy of the potato consists of no less than five ranks. The folk generic rank is composed of three taxa: Araq Papa (semi-wild / consumed), Papa Tarpuy (cultivated / consumed), and Atoq Papa (wild / not consumed). Folk specific taxa (= cultivar groups) and varietal taxa (= cultivars) within the generic taxon of Papa Tarpuy are abundant. Use categories and agroecological criteria are of little importance in the folk taxonomical system of the potato. Folk varietal taxa cluster well when using formal morphological descriptors; folk specific taxa less so. A moderate concordance, albeit with considerable exceptions, exists between folk specific or varietal taxa and their genetic make-up as characterized with molecular markers (18 SSR microsatellites). The coherence of clustering in a dissimilarity tree varies for each folk specific or varietal taxon considered. Farmers use 22 plant and 15 tuber folk descriptors with recognized character states in the Quechua language. Farmers are well able to recognize specific cultivars based on aboveground plant parts only (without exposing tubers). Nomenclature is regionally consistent for common cultivars, while inconsistent for scarce cultivars. Primary cultivar names (nouns) generally refer to a folk specific taxon through predominant metaphorical reference to tuber shape. Secondary cultivar names (adjectives) predominantly provide direct reference to tuber color. Annual spatial patterns Annual spatial management of the potato consists of cropping and labor calendars, field scattering practices, and genotype by environmental management. These three dimensions of agrobiodiversity management are explored in chapter 4. A structured survey was conducted to investigate the potato cropping and labor calendars. Participatory cartography resulted in the detailed mapping of 601 scattered potato fields, including their cultivar content, belonging to a total of 122 households. A genotype by environment (GxE) experiment employing 4 environments and 31 cultivars was conducted following an altitudinal transect. Data obtained was analyzed and interpreted using descriptive statistics, correlation analysis, Geographical Information Systems (GIS), Additive main Effects and Multiplicative Interaction (AMMI) analysis, and analysis of variance (ANOVA). The annual distribution of tasks and labor is primarily an adaptation to the single-season rain-fed character and climate extremes of high-altitude agriculture. Three different footplough-based tillage systems allow farmers to efficiently manage scarce labor availability for soil preparation. Native-floury, nativebitter and improved potato cultivars show considerable overlap concerning their altitudinal distribution patterns. The notion that these cultivar categories occupy separate production spaces (so-called “altitudinal belts”) is rejected as results show that differences between the altitudinal medians for areal distribution by altitude of the different cultivar categories are modest (chapter 4). Field scattering is based on a combined logic which results in a patchy distribution of potato genetic diversity across the agricultural landscape. Depending on the community, farmers annually crop an average of 3.2 to 9.1 potato fields measuring between 660 to 1,576 m² and containing up to a hundred cultivars per field. However, neither field scattering nor the management of high levels of diversity by farmers is a direct consequence of niche adaptation as most cultivars are versatile (chapter 4). Rather, it is suggested that farmers conduct annual spatial management by deploying combined tolerance and resistance traits imbedded in particular cultivar combinations in order to confront the predominant biotic and abiotic stresses present in different agroecologies. Andean farmers manage GxE adaptation for overall yield stability rather than fine-grained environmental adaptation of native cultivars. Dimensions of land use Three specific dimensions of potato land use were researched in order to gain insights into possible contemporary changes affecting the in-situ conservation of potato genetic resources: land use tendencies, rotation designs and their intensity, and sectoral fallowing systems (chapter 5). The main research method involved participatory cartography using printed poster-size high-resolution Quickbird satellite images combined with in-depth consultation through interviews and focus group meetings with members of the communities. A total of 4,343 fields and their 1995-2005 crop contents were mapped. The evolution over a 30-year time-span (1975-2005) of traditional sectoral fallow systems (“diversity hotspots”) was documented for each community. Data was analyzed using descriptive statistics and Geographical Information Systems (GIS). Processes of change and adaptive innovation were documented by building case studies. Land use tendencies between 1995 and 2005 shows that the total cropping area dedicated to improved cultivars has grown fast while the area dedicated to native-floury and native-bitter cultivars has remained more or less stable. Reduced fallow periods for existing fields and the gradual incorporating of high-altitude virgin pasture lands sustain areal growth. Areal growth is particularly fast at extreme altitudes between 3,900 and 4,350 m. However, fallow periods at these altitudes are still relatively long compared to fields at lower altitudes. Results show that fallowing rates increase by altitude for all cultivar categories, but tend to be lowest for improved cultivars followed by native-floury and native-bitter cultivars. There is no evidence of a straightforward replacement of one cultivar category by another resulting in the replacement and loss of infraspecific diversity. Inquiry into the dynamics of sectoral fallow systems over a 30 year period evidences the gradual disintegration and abandonment of these systems rich in cultivar diversity. They are replaced by more individualist management regimes based on household decision making. Nowadays, the spatial patterning of potato genetic diversity within the agricultural landscape is increasingly characterized by patchy distribution patterns rather than its concentration within a single communal sector. Where sectoral rotation designs survive local innovations have been adopted. Farmer seed systems Farmer seed systems can be conceived as an overlay of crop genetic diversity determining its temporal and spatial patterning. Chapter 6 investigates the relation between selected farmer seed system components (storage, health and procurement) and infraspecific diversity of potato in Huancavelica. A sampling exercise was carried out in farmer seed stores in order to gain insight into the internal organization of seed stores and how this relates to the management of infraspecific diversity. Virus infection rates were determined by taking seed tuber samples of diverse cultivars from farmer’s storage facilities. ELISA tests were conduced for APMoV, PLRV, PMTV, PVY and PVX. Seed procurement was investigated through a series of structured surveys focusing on household seed exchange, the role of regular markets and biodiversity seed fairs, and seed provision after severe regional frost. Data was analyzed and interpreted using descriptive statistics. Potato seed stores contain different seed lots, reflecting the rationales underlying management of cultivar diversity at the field level and the overall structure of infraspecific diversity. Seed health of farmer conserved cultivar stocks in Huancavelica is affected by Diabrotica leaf beetle and contact transmitted viruses (APMoV, PVX) while aphid and powdery scab transmitted viruses (PMTV, PLRV, PVY) are of limited importance. During normal years without extreme events seed exchange of native-floury cultivars is practiced by few households and characterized by a limited number of transactions involving small quantities of seed of few cultivars covering relatively short distances. Native-bitter and uncommon nativefloury cultivars are rarely exchanged and generally reproduced year after year by the same households that maintain them. High-altitude diversity-rich communities tend to be net seed exporters. However, the capacity of the farmer seed system to annually widely supply and distribute infraspecific diversity is limited. Regular markets have a decentralized capacity to supply and widely distribute seed of a limited number of well-known cultivars. Frequencies of seed exchange at biodiversity seed fairs are low and involve small quantities of a few uncommon cultivars. The resilience of the farmer seed system to cope with severe regional seed stress is insufficient for households to be able to restore volumes and cultivar portfolios within a short period of time. The potato-based food system The role of biodiverse potatoes within the human diet in Huancavelica is investigated in chapter 7. Analysis to determine the dry matter, gross energy, crude protein, iron (Fe) and zinc (Zn) content of 12 native-floury cultivars (fresh / boiled tuber samples) and 9 native-bitter cultivars (boiled unprocessed / boiled processed tuber samples) was conduced. Additionally, the nutritional composition of the native-floury cultivars was determined after 3 and 5 months of storage under farmer conditions. A food intake study was conducted during two contrasting periods of food availability (abundance versus scarcity) in order to quantify and characterize the contribution of the potato, different cultivar categories and other food sources to the diet of children between 6 and 36 months of age and their mothers. The specific method consisted of direct measurement of food intake by weight during a 24 hour period for each household (77 households). Further, the overall nutritional status of 340 children aged between 4 and 16 years was determined. Selected cultural connotations of the highland diet were investigated through participant and ethnographic observation, surveys, and workshops. Results show that several native-floury cultivars contain higher contents of specific nutrients (protein, iron) than those commonly reported as representative for native potato cultivars. This suggests that infraspecific diversity can make a valuable contribution to enhanced nutrition. Storage does not affect the nutritional quality of native-floury cultivars very significantly while traditional freeze-drying of native-bitter cultivars considerably reduces protein and zinc content. The research shows that malnutrition in Huancavelica is primarily a consequence of micronutrient deficiency and secondarily of insufficient total energy coverage. The highland diet is heavily dependent on staple foods, particularly potato and barley, and generally short in vegetable, fruit, meat and milk intake. The potato contributes significantly to the nutritional balance and the recommended requirements for energy, protein, iron and zinc of women and children during periods of both food abundance and scarcity. Improved and native-floury cultivars complement each other as each category provides the bulk of potatoes consumed at different moments in time. The consumption of diverse potato cultivars is entangled with cultural constructions of meals and local perceptions of preference traits and quality. The potato itself, as a food item, is no socioeconomic class marker. However, certain dishes or products and the overall cultivar diversity grown and used by a household shape perceptions of relative wealth. Conclusions and implications Chapter 8 highlights the main conclusions of the study and provides answers to the original research questions while taking the different system levels explored throughout the thesis into account. Selected priority areas of future research are identified and, where appropriate, links to other parts of the Andes are drawn. Furthermore, the implications for externally driven R&D oriented in-situ conservation efforts seeking to support dynamic and ongoing farmer-driven conservation are discussed. It is argued that the science and practice of R&D oriented in-situ conservation lag behind the policy commitments to its implementation and that institutional learning from diverse projects already implemented throughout the Andes and the diffusion of key lessons is essential for the success of future interventions

Small ruminant production in the humid tropics

Research review on sheep and goat production in the humid zone of West Africa, w. respect to animal population, production parameters, reproduction, forage production, supplementary feeding based on agro - industrial byproducts, disease incidence, particularly peste petits ruminants & helminthiasis, housing, and economic aspects of small and large scale production, w. proposals for further research