Children’s School Achievement and Parental Work: an analysis for Sweden

In this paper, data from Statistics Sweden about students entering upper secondary school (10th grade) in 1994 and graduating in 1996 or 1997, along with socioeconomic characteristics from the 1990 census, are used to explore the relationship between the market work by mothers and fathers in Sweden and their children’s educational achievement, measured as Grade Point Average. The results show, in line with previous research, that there is a positive relationship between parental income and child GPA. When it comes to the number of hours of work that the parents perform in the labour market, the results differ between mothers and fathers. If the mother works less then full time, preferably even less then halftime, it has positive effects on the child’s grades. There are no significant effects of the father’s hours of work, as long as he works a positive amount of time. The lack of effects from the father’s hours of work may, however, be due to lack of variation in data.Time allocation; labour-force participation; educational achievements; child GPA

Optimised control of Stark-shift-chirped rapid-adiabatic-passage in a lambda-type three-level system

Inhomogeneous broadening of energy levels is one of the principal limiting factors for achieving "slow" or "stationary" light in solid state media by means of electromagnetically induced transparency (EIT), a quantum version of stimulated Raman adiabatic passage (STIRAP). Stark-shift-chirped rapid-adiabatic-passage (SCRAP) has been shown to be far less sensitive to inhomogeneous broadening than STIRAP, a population transfer technique to which it is closely related. We further optimise the pulses used in SCRAP to be even less sensitive to inhomogeneous broadening in a lambda-type three-level system. The optimised pulses perform at a higher fidelity than the standard gaussian pulses for a wide range of detunings (i.e. large inhomogeneous broadening).Comment: 6 pages, 6 figures, 1 tabl

Simulation and measurement of the dynamics of ultra-short electron bunch profiles for the generation of coherent THz radiation

The shape of an electron bunch has a tremendous impact on its emission of synchrotron radiation. Especially the formation of sub-structures can increase the yield in the THz region. This thesis investigates the micro-bunching instability, a mechanism where structures form due to self-interaction of the electrons with their own wake-field. The methods include simulation and measurements. On the simulation side, the thesis describes the optimization of simulation algorithms to increase numerical stability as well as computational performance. On the experimental side, an optimized monitor for single-shot bunch profile measurements was designed to allow continuous bunch profile measurements with high signal-to-noise ratio and a sub-ps resolution at 2.7 MHz repetition rate

Turbulence and aeolian sand transport

A description and some results of the calculated aeolian sand transport including the turbulence intensity and the autocorrelation of the wind field in the transport equation’s are presented in this study. The simulated transport related to Sørensen (2004) transport equation varies by more than 100% for one and the same friction velocity and one and the same sand type near the thresholds by variation of turbulence intensity and/or the autocorrelation of the wind. Published results of sand transport measurements are imperfect and not comparable without information about the characteristics of the turbulent wind. An indication of friction velocity, threshold friction velocity and measured transport must be supplement by the specification of the turbulence intensity and the autocorrelation of the wind velocity

The Phase-Out of the Nuclear Family? Empirical Studies on the Economics and Structure of Modern Swedish Families.

This thesis consists of three papers on the economics and structure of Swedish families. Paper [I] examines the determinants of children’s educational achievement in Sweden. Special attention is given to the labour market work by mothers and fathers in terms of its influence on the educational outcome of their children, measured as grade point average (GPA) in compulsory as well as upper sec-ondary school. The results show that there is a positive relationship between parental income and GPA. Regarding the number of hours worked in the la-bour market, the results differ between mothers and fathers. Having a mother that works less than full time has positive effects on the child’s grades throughout the schooling of the child, whereas significant effects of the hours of work that the father puts in are found during upper secondary school only. Paper [II] explores the role of financial surprises and match quality in the dis-solution of relationships. The analysis is carried out both for surprises in the short term earnings and surprises in the long-run earnings capacity. It is found that positive surprises in short term earnings have a destabilizing effect for a relationship. Generally, a negative surprise in long-run earnings capacity for males has a destabilizing effect. However, if it is combined with a female positive surprise, the effect is stabilizing. Commitments become more stable the older the spouses are at the start, and if young children are present. Paper [III] studies the role of unemployment in the dissolu¬tion of relationships by applying a two-step estimation method to an extensive data set, which con-tains information about young Swedish males and females. Unemployment is recognized as endogenous in the separation decision, and the results show that the effect of unemploy¬ment on separation is biased when unemployment is assumed to be exo¬genous in the separation equation. The probability of sepa-ration is found to be increasing with male unemployment, while female un-employment decreases the probability of dissolution.Time allocation; labour-force participation; educational achievements; match quality; financial surprises; unemployment; divorce; family structure

Ejection and impact angles of saltating particles measured with a high-speed camera

3D and 2D trajectory data of sand grains saltating over a bed are presented from highspeed camera measurements. They were obtained at Zingst peninsula and in laboratory using a wind tunnel. Trajectories, calculated with a Runge-Kutta procedure, using values of the mean wind profile and the air flow were fitted to the measured ones. The trajectory with the lowest RMSE against the measured one was used to estimate the grain diameter of the saltating grain. Also ejection and impact angle, ejection and impact speed of the grain were determined. The results confirm earlier findings that ejection angles decreases with increasing grain diameter. Ejection angles between 57° and 27° for fine (63-200 μm) and middle (200-630 μm) ejecta and between 38° and 20° for coarse grains (630-2000 μm) were found. The impact angle β increases with increasing grain diameter. Impact angles between 8° and 15° for fine impactors and between 12° and 36° for middle and coarse grains were found. Additionally the ratio between the mean ejection angle α and mean impact angle β, which decrease with increasing grain diameter (Rice et al., 1995), could be confirmed. The ration between the ejection speed ue and impact speed ui was found nearly the same for all determined grain sizes, but the grains ejected from the bed had an average speed of one order of magnitude less than the impact speed

Fatty acids in beef from grain- and grass-fed cattle: the unique South African scenario

Objective: Different fatty acids elicit different responses in the human body once ingested. Although red meat is often considered to be a source of fatty acids which has a negative impact on human health, many studies have reflected variability in the quantity and quality of fatty acids found in red meat produced on different production systems in different countries. This study evaluated the fatty acid profile of beef, produced by the grass- and grain-fed production systems practised in South Africa.Design: Data are reported as a percentage of lipid per 100 g total fat to enable a comparison with international findings. Furthermore, the findings are translated into edible meat portions, taking fat trimming (often associated with red meat intake) into consideration in order to determine the contribution which the different products can make to the human diet.Subjects and setting: Three cuts of beef from cattle from four production groups were sampled and the fatty acid composition analysed for the meat and fat fractions.Results: Notable differences were found in the quantity and quality of different fatty acids in beef from the different production systems. When untrimmed, no statistically significant difference was found in the total fat between beef produced on the different production systems. Differences became more significant as trimming was performed. When trimmed of all visible fat, beef from young cattle fed according to a grain-based feeding system contained less total fat (6.96 g), and less saturated fat (2.16 g) per 100 g, than beef produced from their grass-fed counterparts (9.77 g and 3.30 g, respectively). There was a more favourable omega-6 to omega-3 fatty acid ratio, i.e. 2.0–2.5:1.0 for grassfed cattle, compared to 8–30:1 for grain-fed cattle, irrespective of the degree of trimming. The beef from the grass-fed cattle also contained a higher quantity of conjugated linoleic acid.Conclusion: A unique classification system for red meat has been implemented in South Africa and dictates the characteristics of the fresh meat that is available to consumers. The results of this study consequently indicate distinctive differences between the fatty acid profile of local red meat and that of beef produce from other countries; often used as a reference for dietary guidance.Keywords: grain fed, grass fed, cattle, fatty acids, red mea

Nutrition-Sensitive Agricultural Development for Food Security in Africa: A Case Study of South Africa

The paradox of persistent under‐nutrition and food insecurity; as well as the increasing the incidence of over nutrition is particularly observed in middle –income countries experiencing rapid westernisation such as South Africa (SA). Values of household Food insecurity remains high, whereas overweight and obesity are increasing at a rapid rate. Agriculture and the food system play a key role in nutrition, health and food security. It provides for the primary sources of energy along with essential nutrients, while simultaneously being a source of income, creating jobs and earning foreign exchange. This case study presents the current nutrition sensitivity of the South‐African agriculture and food systems (including governmental prioritization) and highlights the importance of this for future development towards improved food and nutrition Security and nutritional status. Since 2013, discussions on a single, comprehensive, food security and nutrition policy and implementation plan for South Africa have been in process with the aim to coordinate the improvement of both food security and all forms of malnutrition. Yet, the case study findings indicate an unfortunate lack of understanding about nutrient density and dietary diversity and the role which this could play in combating non‐communicable diseases in addition to food insecurity and hunger