This thesis concerns the use of nuclear reactions to study the structure of neutron-rich light nuclei. Emphasis is placed on 11Be which has been identified as a nucleus with a single neutron halo and which offers a simple 2-body case for detailed analysis. Comparisons are made with experimental data for the break-up of 11Be on gold, titanium and beryllium targets. As a prelude to more detailed work a simple elastic break-up model calculation, using the Distorted Wave Born Approximation (DWBA), is attempted. The resulting theoretical cross-sections show good agreement with the shape of the experimental data but cannot predict the absolute magnitude. A major part of the break-up work is a more accurate model using the post-form DWBA. The formulation is built up from basic scattering theory and includes details of employing the Zero Range Approximation and the Vincent and Fortune method of integration. A Finite Range Correction is also applied. Cross-section calculations for a gold target agree closely with experiment but a problem arises for lighter targets. Here the Coulomb potential must be excluded from the calculation to obtain a result that matches the experimental data. A method for the calculation of inelastic break-up is presented which only requires a small modification to the methods used for elastic break-up. As it suffers from the same light target problem only calculations for a gold target give an inclusive cross-section, produced from the elastic and inelastic contributions, which matches the experimental data satisfactorily. To overcome the light target problem a full recoil calculation is introduced. Arguments and analysis are produced to show that this method is too demanding of both computing time and storage for practicable implementation. Future calculations are proposed using an analytical method for Coulomb break-up.

The wavelength dependence of the integrated and peak reflectivities of distorted copper single crystals has been measured and the results compared with calculated values obtained from Bacon and Lowde's model of an ideally imperfect mosaic crystal. The effects of simultaneous reflections on the reflected neutron intensities were studied and accounted for in terms of an effective absorption coefficient. A non-Gaussian mosaic block distribution function was successfully introduced to bring about better agreement between experimental and calculated curve shapes. Using this technique, the desired agreement in curve shape was attained but, in order to bring measured and calculated absolute reflectivities into better agreement, it was necessary to include primary extinction effects. / Thesis / Master of Science (MSc)

Thesis advisor: James E. Anderson / Thesis advisor: Rosen Valchev / The effect of uncertainty on firms' behavior and on the macroeconomy is generally negative in the literature. Extensive research has also demonstrated that financial frictions limit the extent of firms' activities and growth prospects. In the first two chapters of this dissertation, I study both empirically and theoretically how a specific type of uncertainty, exchange rate uncertainty, interacts with financial frictions to affect the behavior of exporting firms. In line with the existing literature, I find in the first chapter that exports of manufacturing sectors in which firms are more financially constrained decrease by more in times of high uncertainty. Having more tangible capital, which can potentially be used as collateral, makes the effect of uncertainty less negative, especially im sectors where firms are large. Relying more on external financing, on the other hand, makes the effect more negative and affects sectors with small firms more. Current theoretical models have little to say about the effect of uncertainty on heterogeneous firms. To address this issue, I introduce in the second chapter a model of financially-constrained heterogeneous exporting firms in which credit conditions depend on the degree of exchange rate uncertainty. Firms in different sectors face different types of financial constraints, and are therefore differently affected by uncertainty. I use the calibrated model to evaluate potential policies that could be implemented to alleviate the negative effect of exchange rate uncertainty on exports. The uncovered interest parity puzzle is the empirical finding that countries with higher risk-free interest rates tend to see their currencies appreciate in the short run. Typical two-country macroeconomic models instead predict that high interest-rate currencies depreciate, with arbitrage opportunities eliminating profitable carry trade strategies. The international finance literature responded to this puzzle by providing several alternative theoretical models able to explain the puzzle. In the third chapter of this dissertation, I study how the predictions of two of these alternative models - the habit model of Verdelhan (2010) and the distorted belief model of Gourinchas and Tornell (2004) - are affected when re-cast in a standard dynamic stochastic general equilibrium framework. I investigate how the mechanisms rely on specific parameter values in order to find under which conditions, if any, they can explain the UIP puzzle. In addition, I obtain business cycle moments from model simulations and compare them to the moments obtained from a standard two-country DSGE model and from the data. My results show that for the first model, the habit model, the UIP results disappear under realistic calibrations. For the second model, the distorted beliefs model, UIP properties remain under some calibrations. In addition, business cycle predictions remain close to empirical evidence. / Thesis (PhD) — Boston College, 2019. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Economics.

<p>I större städer är det vanligare med stress, oro och ångest. Av den anledningen fanns det skäl att tro att individer i storstäder skiljde sig från individer på landsbygden även gällande annan psykisk ohälsa. Studiens syfte var att undersöka om det fanns någon skillnad i ungdomars självrapporterade ätbeteende respektive kroppsuppfattning beroende på urbanisationsgrad, kön och BMI. Deltagarna i undersökningen var 140 gymnasieelever indelade i två grupper, storstad och tätort, utifrån urbanisationsgrad. Undersökningsmaterialet bestod främst av The Eating Attitudes Test (EAT-26), några frågor från Eating Disorder Inventory-2 samt Figure Rating Scale. Resultaten visade att det inte fanns någon skillnad i ungdomars ätbeteende respektive kroppsuppfattning beroende på urbanisationsgrad, men däremot beroende på kön och BMI.</p>

The main objective of this thesis is to study the behavior of black objects in external fields, for example black holes and black strings in 4 and 5-dimensional spacetimes respectively. In particular, to analyze how external fields affect horizons and the internal structure of such objects, to study their properties, and tocunderstand how the spacetime fabric works. The thesis contains three chapters. In Chapters 1 and 2 we study the interior of 4-dimensional static, axisymmetric, electrically neutral and electrically charged distorted black holes. We analyze how external static and axisymmetric distortions affect the interior of such black holes. In particular, we study the behavior of the interior solution of an electrically neutral black hole near its horizon and singularity. The analysis shows that there exists a certain duality between the event horizon and the singularity. As a special example, we study the interior of a compactified 4-dimensional Schwarzschild black hole. In the case of an electrically charged black hole, a similar duality exists between its event and Cauchy horizons. The duality implies that the Cauchy horizon remains regular, provided the distortion is regular at the event horizon. Extension of the general theory of relativity to higher dimensional spacetimes brings a large variety of black objects whose boundary, the event horizon, may be of a complicated structure. One such object is a black string. In Chapter 3 we discuss the so-called Gregory-Laflamme instability of 5-dimensional black strings in a spacetime with one compact dimension and their topological phase transitions. Here we consider black strings with electric or magnetic charge. Linear static perturbations of these objects indicate the presence of a threshold unstable mode. An analysis of such mode shows that an electrically charged black string is less stable than a neutral one. The situation is opposite for a magnetically charged black string. An analysis of 5-dimensional extremal black string with electric charge shows a continuous spectrum of unstable threshold modes. The results presented in this thesis may have applications in the theory of classical 4-dimensional black holes and in the modern theoretical models of higher dimensions.

I större städer är det vanligare med stress, oro och ångest. Av den anledningen fanns det skäl att tro att individer i storstäder skiljde sig från individer på landsbygden även gällande annan psykisk ohälsa. Studiens syfte var att undersöka om det fanns någon skillnad i ungdomars självrapporterade ätbeteende respektive kroppsuppfattning beroende på urbanisationsgrad, kön och BMI. Deltagarna i undersökningen var 140 gymnasieelever indelade i två grupper, storstad och tätort, utifrån urbanisationsgrad. Undersökningsmaterialet bestod främst av The Eating Attitudes Test (EAT-26), några frågor från Eating Disorder Inventory-2 samt Figure Rating Scale. Resultaten visade att det inte fanns någon skillnad i ungdomars ätbeteende respektive kroppsuppfattning beroende på urbanisationsgrad, men däremot beroende på kön och BMI.

No description available.

Powerful classifiers as neural networks have long been used to recognise images; these images might depict objects like animals, people or plain text. Distorted images affect the neural network's ability to recognise them, they might be distorted or changed due to distortions related to the camera.Camera related distortions, and how they affect the accuracy, have previously been explored. Recently, it has been proven that images can be intentionally made harder to recognise, an effect that last even after they have been photographed.Such images are known as adversarial examples.The purpose of this thesis is to evaluate how well a neural network can recognise adversarial examples which are also distorted. To evaluate the network, the adversarial examples are distorted in different ways and thereafter fed to the neural network.Different kinds of distortions (rotation, blur, contrast and skew) were used to distort the examples. For each type and strength of distortion the network's ability to classify was measured.Here, it is shown that all distortions influenced the neural network's ability to recognise images.It is concluded that the type and strength of a distortion are important factors when classifying distorted adversarial examples, but also that some distortions, rotation and skew, are able to keep their characteristic influence on the accuracy, even if they are influenced by other distortions.

Much of what has been researched on Shona fiction has been limited to literature published before independence. The current research endeavours to assess the treatment of socio-economic issues as conveyed through fiction published since 1990. This fiction focuses on socio-economic issues in both pre-colonial and independent Zimbabwe. The study endeavours to establish if writers who focus on these issues in the pre-colonial era have been able to reclaim a complicated picture of the African pasts. It also discusses fiction that focuses on post-independence experiences; such as extent of the impact of empowerment brought about by independence, continued poverty among Africans, emancipation of the female being and the HIV and AIDS pandemic. Here, it strives to ascertain if the writers have identified the causes and offer meaningful solutions to these. The study observes that contemporary novelists on the Shona pasts have reclaimed more realistic ‘worlds’ when compared to their predecessors who have largely presented distorted images of these pasts. On the outcome of independence, two groups portray it as a total success and a total failure respectively, whilst the third and more successful group gives a balanced exposition. Fiction on poverty among contemporary Africans falls into two classes, namely rural and urban. The former still suffers from the heavy influence of colonial myths as it only highlights the effects of poverty without situating them in their tension-ridden historical context. The latter provides important sociological information on the plight of the characters but is lacking when it comes to suggesting ways of alleviating such poverty. On female empowerment, it emerges that while some writers are for women empowerment, others are against it. Women writers are better at explaining problems of women. However, both groups are still unable to identify the root cause of the incapacitation of women. On HIV and AIDS, whilst male writers demonstrate a wider social vision on the factors that disempower society against the spread and curbing of the virus, female authors still fall in the trap of blaming both men and Shona traditional customs. Overall, it emerges that contemporary Shona writers reveal contradictory modes in articulating these issues. / African Languages / Thesis (D. Litt et Phil. (African Languages))

Thesis (PhD)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: See fulltext for abstract. / AFRIKAANSE OPSOMMING: Sien volteks vir opsomming.