• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 1067
  • 521
  • 360
  • 143
  • 128
  • 99
  • 51
  • 32
  • 26
  • 21
  • 16
  • 13
  • 13
  • 13
  • 13
  • Tagged with
  • 2950
  • 1603
  • 965
  • 680
  • 313
  • 260
  • 244
  • 228
  • 206
  • 193
  • 183
  • 169
  • 163
  • 147
  • 113
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
121

Structure and Dynamics of the Hepatitis B Virus Encapsidation Signal Revealed by NMR Spectroscopy

Flodell, Sara January 2004 (has links)
This thesis describes the study of the three-dimensional structure and dynamics of the hepatitis B virus (HBV) encapsidation signal, epsilon, by means of nuclear magnetic resonance (NMR) and mutational data. HBV replicates by reverse transcription of an RNA pregenome into the viral DNA genome, which becomes enclosed in viral particles (encapsidation). Epsilon is a stem-loop structure within the RNA pregenome and both the primary sequence and secondary structure of epsilon are strongly conserved, in agreement with its essential function of propagating HBV. Epsilon is therefore a potential target for drug design. Studying the structure of epsilon requires development of new methods in the field of structural biology, as it is such a large RNA. Knowing the structure of epsilon will help to better understand the encapsidation mechanism and priming step of reverse transcription. This will help us in the search for antiviral drugs that block epsilon and prevent the viral reverse transcriptase from binding. NMR spectroscopy is a method that provides detailed structural and dynamical data in solution under natural conditions. However, the size of the molecules that can be studied with NMR is limited. NMR spectra become more and more difficult to interpret as the size of the molecule increases. To circumvent this problem, large RNA molecules can be divided into smaller parts and only the parts essential for NMR studies are selected. The information obtained from these smaller fragments can then be used to determine the structure of the larger molecule. Furthermore, a new method of enzymatically synthesizing nucleoside triphosphates with isotopes suitable for NMR has made it possible to specifically label the RNA molecules. Using this method it is possible to derive highly detailed molecular structures of RNA up to a size of 150 nucleotides. The method of selective isotope labelling was applied to different parts of HBV epsilon. Three RNA fragments of 27 (apical loop), 36 (internal bulge) and 61 (whole epsilon) nucleotides (nt) were synthesized in the unlabelled form. The 27-nt and 36-nt RNAs were also synthesized with (13C, 15N, 1', 3', 4', 5', 5"-2H5)-labelled uridines. The 61-nt sequence was (13C, 15N)-guanidine labelled. This labelling allowed unambiguous assignment of otherwise inaccessible parameters. The unlabelled and labelled RNA sequences provided the necessary data for structure derivation of the whole epsilon. The apical loop of epsilon forms a pseudo-triloop motif. There is only one conformation of the loop that fulfils all the restraints, including experimental chemical shifts. However, the loop adopts several structures that fulfil the experimental distance, torsion angle and residual dipolar coupling restraints. This may reflect true flexibility. Indeed, relaxation studies on the unlabelled and labelled 27-nt sequences show that the residues that show multiple conformations are flexible. This can be an important feature for the recognition and subsequent binding of epsilon to the viral polymerase. The information gained on the HBV encapsidation signal is useful in our understanding of the initiation of replication of the virus. This can in turn contribute to the search for drugs against HBV.
122

The dielectric properties of solid biofuels

Paz, Ana Marta January 2010 (has links)
The use of bioenergy has been increasing due to efforts in fossil fuels replacement. Modern bioenergy technologies aim for high efficiency and low pollution levels, which increases the need for methods for the on-line characterization of biofuels. Dielectric methods have been identified as useful for the sensing of solid biofuels because they allow for rapid, nonhazardous, nondestructive, and bulk determination of material properties. The dielectric properties describe the interaction between the material and the electromagnetic waves. Dielectric properties are intrinsic of the materials and can therefore be used for the development of prediction models that can be applied regardless of the measurement technique. The study of the dielectric properties is also important as it improves the understanding of the dielectric behavior of the materials. This thesis focuses on the dielectric properties of solid biofuels and their use in the characterization of these materials. The work presented includes the development of new methods permitting the determination of the dielectric properties of solid biofuels with large particle size (waveguide method), broadband measurement of the dielectric properties (coaxial-line probe), and the use of a previously developed method for the accurate determination of the dielectric properties (free-space method). The results includes the dielectric properties of solid biofuels and their dependence on parameters such as frequency, moisture, density, and temperature. This thesis also presents semi-theoretical models for the determination of moisture content, which obtained a RMSEP of 4% for moisture contents between 34 and 67%, and an empirical model that resulted in a RMSEC of 0.3% for moisture contents between 4 and 13%. Finally, this thesis includes measurements of the influence of salt content on the dielectric properties and a discussion of its use for estimation of the ash content of solid biofuels. 
123

Skog för export : skogsarbete, teknik och försörjning i Lule älvdal 1870-1970 / Timber for export : forest work, technology and income in the Lule Valley 1870-1970

Lundgren, Nils-Gustav January 1984 (has links)
The forestry industry played an important role in the industrialization of the Swedish economy in the late 19th century. The aim of this study is to deed with the determination of income and wages in the forestry regions where the sawmills and pulp industries found their raw material supplies.The formation of incomes and wages for lumberjacks and drivers is analysed in the Parish of Jokkmokk in the far north of Sweden for the period 1878 to 1938. The number of workers engaged in forestry is also estimated as is the total labour supply in the parish.Technological development and productivity in felling and transportation are analysed. This part of the study covers the period 1880 to the present, and includes log-driving activities on the Lule River from 1881 to 1977.Briefly, the findings of the study are that income, timber prices and wages in forestry in the parish fluctuated together with exports of forestry products, particularly pulp after the year 1910. Estimates also show that troughs were deeper and booms more marked in the study area than in the overall market for forestry products measured both in volume and in export value.Labour productivity in felling and transport showed a rising tendency in the last two decades of the 19th century, which reflects the replacement of the axe as the only instrument for felling by the two-man timber saw. Better horses, fodder and sledges also raised efficiency.However, during the first half of the 20th century, labour productivity was markedly stagnant. Improvements in equipment, such as better steel in the saws, even stronger horses and so on, could not compensate for circumstances such as longer transporting distances and more cutting in the forests with lower volume per tree.These latter tendencies reflect a growing shortage of raw materials which the Swedish forestry industries had to face from about the turn of the century. Not until about 1955, when tractors replaced horses and the power saw replaced the one-man timber saw, did productivity rise substantially. Over a period of fifteen to twenty years, forestry work became almost completely mechanized.The labour force in the Parish of Jokkmokk was over 2,000 men in the boom of the 1930s. Today, the labour force is a steady 250 or so. The technological change in the 1960s was, of course, an adjustment to the extremely high labour costs in the Swedish post-war economy.In industry, a continuous adjustment to the factor proportions in the economy had taken place. In forestry, adjustment took place over a very short period of time after decades of stagnation from the technological point of view. Institutional, social and technical obstacles had delayed adjustments earlier. A totally new organization within forestry work was required before new techniques could be introduced. These were not applicable to older organization forms based on part-time farmers, part-time foresters. / digitalisering@umu
124

The Implications of Relational Activity Motivations for Relationship Well-Being and Daily Relational Functioning in Marriage

Gaine, Graham Sherwood January 2011 (has links)
People experience autonomy when they perceive their behaviour to be volitional and they feel controlled when their behaviour is driven by external demands or internal pressures. Gaine and La Guardia (2009) developed the Motivations for Relational Activities (MRA) scale to assess the extent to which romantic partners feel autonomous and controlled in a variety of specific relational activities. In a sample of mostly non-married individuals, Gaine and La Guardia (2009) found that the more willing and the less pressured individuals feel to engage in relational activities, the greater their relationship well-being. Study 1 examined whether autonomous and controlled activity motivations have similar implications for relationship well-being for married individuals. Results replicated the results from the non-married sample (Gaine & La Guardia, 2009). Study 2 assessed the relational activity motivation of both partners in married and common-law relationships and examined how one’s own motives relate to one’s own relationship well-being and one’s partner’s relationship well-being. Results suggested that one’s own motivations toward relational activities predict one’s own relationship well-being but not one’s partner’s well-being, with the exception of men’s relationship satisfaction, which was positively predicted by women’s autonomous activity motivation. Study 2 also employed daily diaries to examine the implications of each partner’s activity motivations for partners’ daily relational functioning and well-being. Results showed that when individuals are more willing and less pressured to engage in relational activities, they experience greater daily relationship well-being. Further, when individuals are more willing and less pressured in their relational activities, they are observed by their partner to be more engaged and responsive on a day-to-day basis. Finally, women’s willing engagement of relational activities emerged as a particularly important predictor of their own as well as men’s relational functioning and wellness.
125

You must be creative! The effect of performance feedback on intrinsic motivation and creativity

Benzer, Justin Kane 15 May 2009 (has links)
Feedback sign (positive, negative, or no feedback sign) and feedback style (autonomous, controlling, or no feedback style) were manipulated in a 3x3 repeated measures design. Two hundred thirty-three undergraduate students from introductory psychology classes completed measures of perceived competence, perceived choice, and interest over four time periods. Interest was regressed on perceived competence, perceived choice, and a moderation analysis revealed that perceived choice moderated the effect of perceived competence on interest. Creative answers to open-ended problems were assessed after time 2 (before feedback), and after time 3 (after feedback). Feedback style (autonomous, controlled, and neutral) and Feedback sign (positive, negative, and neutral) manipulations were analyzed using a 3x3 ANOVA, revealing no effect of feedback. Post-hoc analyses using perceived difficulty of the first creative problem as a covariate revealed an interaction of feedback style and difficulty, limiting between subjects analyses. Creativity was also regressed on interest. Pre-feedback interest predicted creativity according to expectations, but post-feedback interest did not predict creativity. Creativity did predict post-performance interest, possibly implying that interest is not a valid proxy for intrinsic motivation in within-subjects designs. Future studies should test the proposition that feedback affects intrinsic motivation, which in turn affects creative performance, and creative performance affects interest.
126

The Empirical assessment of Portfolio Balance Model

Chen, Kai-wen 26 June 2007 (has links)
Using asset prices to explain the fluctuations of nominal exchange rate is popular for decades. A majority of papers focused on Monetary Model but failed to make a consistent conclusion. In this article, we suggest that the failure of monetary model might be coming from the basic assumption of taking different countries¡¦ assets as ¡§perfect substitutes¡¨. Under such circumstances, we introduce another model named as ¡§Portfolio Balance Model¡¨ where assets of different countries are no longer be taken as ¡§perfect substitutes¡¨ , implying that UIP( Uncoverd Interest Rate Parity)exist no more either. We do not overthrow the entire theory of Monetary Model. Instead, we expect the combination of these two models will turn something out that can be much more general, consistent, and robust. We take Canada as our domestic currency and adopt Johansen(1988) and Stock & Walson(1988) by using co-integration to test on three exchange rates relation (USD/CAD,GBP/CAD,JPY/CAD) from 1973 Q1 to 2004 Q4. It turns out that most of the coefficient are correct and passing statistical significance, such result suggest that the portfolio balance effect should not be ignored in the model.
127

RISK DISCLOSURE IN SECURITIES EXCHANGE AND MEDICAL TREATMENT CONTRACTS

IIJIMA, YOSHIHIKO 02 1900 (has links)
No description available.
128

Giving Back and Developing Connections: Supports for Self-Determination and Initiative In a College Leadership Group

Opersteny, Martha G. 14 January 2010 (has links)
The developmental period of adolescence typically refers to the years between 13 and 19, and is associated with developmental tasks that help youth become young adults. The transition to adulthood is typically recognized by common adulthood benchmarks such as leaving home, finishing school, marriage, financial independence and having children. However, many young men and women attending college remain financially and emotionally dependent on their parents, as they have not entered the professional work ranks and are faced with the challenges of college. Increasingly, colleges and universities are becoming places to help teach young people to become prepared for the professional ranks and engaged with the world that surrounds them. However, very little research in higher education is focused on the developmental benefits associated with the college experience. The purpose of this study was to examine the presence of developmental supports for self-determination and initiative in a student leadership program. Throughout the youth development literature, self-determination and initiative are recognized as important internal capacities that aid young people as they transition to adulthood. These concepts provide the theoretical lens for a qualitative case study of a college leadership group. Data were gathered through in-depth semi-structured interviews, observations, a year end focus group, and supplemented by a review of the organizational instruments and tools they develop. Findings from this study confirm past studies of youth development organizations and extend this work by applying it to the developmental period of emerging adulthood. For the leadership group under investigation, initiative and self-determination were supported primarily through the actions of peers within the group. The experience of student leaders often shaped how the group was led, and these leaders became an important source of support for the basic needs of relatedness, competence, and autonomy within the group. The study covers a three-year period, and contrasts how peer leadership changed and impacted group functioning and performance over time. Practical implications of the study relate to the important role of faculty and graduate student advisors in training and monitoring student leaders before these individuals take a formal leadership role for these groups.
129

Fate's grim intervention : determining sibling relationships and mechanisms of cell fate specification in the NB7-3 lineage of the Drosophila embryonic CNS /

Karcavich, Rachel Elaine. January 2001 (has links)
Thesis (Ph. D.)--University of Oregon, 2001. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 99-105). Also available for download via the World Wide Web; free to University of Oregon users.
130

Pitanje samouprave Srbije 1791-1830. Prilog izučavanju stvaranja srpske buržoaske države

Đorđević, Miroslav R. January 1972 (has links)
Thesis--Sarajevo, 1952. / At head of title: Miroslav, R. Đorđević. Includes bibliographical references.

Page generated in 0.1425 seconds