Showing papers by "Norwegian University of Science and Technology published in 2003"

Academic Self-Concept and Self-Efficacy: How Different Are They Really?

Abstract: Academic motivation researchers sometimes struggle to decipher the distinctive characteristics of what appear to be highly analogous constructs. In this article, we discuss important similarities between self-concept and self-efficacy as well as some notable differences. Both constructs share many similarities such as centrality of perceived competence in construct definition; use of mastery experience, social comparison, and reflected appraisals as major information sources; and a domain-specific and multidimensional nature. Both predict motivation, emotion, and performance to varying degrees. However, there are also important differences. These differences include integration vs. separation of cognition and affect, heavily normative vs. goal-referenced evaluation of competence, aggregated vs. context-specific judgment, hierarchical vs. loosely hierarchical structure, past vs. future orientation, and relative temporal stability vs. malleability. We argue that self-efficacy acts as an active precursor of self-concept development and suggest that self-concept research separate out its multiple components and subprocesses and invest more effort toward making students less preoccupied with normative ability comparisons in school.

Bayesian linearized AVO inversion

Abstract: A new linearized AVO inversion technique is developed in a Bayesian framework. The objective is to obtain posterior distributions for P‐wave velocity, S‐wave velocity, and density. Distributions for other elastic parameters can also be assessed—for example, acoustic impedance, shear impedance, and P‐wave to S‐wave velocity ratio. The inversion algorithm is based on the convolutional model and a linearized weak contrast approximation of the Zoeppritz equation. The solution is represented by a Gaussian posterior distribution with explicit expressions for the posterior expectation and covariance; hence, exact prediction intervals for the inverted parameters can be computed under the specified model. The explicit analytical form of the posterior distribution provides a computationally fast inversion method. Tests on synthetic data show that all inverted parameters were almost perfectly retrieved when the noise approached zero. With realistic noise levels, acoustic impedance was the best determined parameter, ...

Human uracil-DNA glycosylase deficiency associated with profoundly impaired immunoglobulin class-switch recombination.

Abstract: Activation-induced cytidine deaminase (AID) is a 'master molecule' in immunoglobulin (Ig) class-switch recombination (CSR) and somatic hypermutation (SHM) generation, AID deficiencies are associated with hyper-IgM phenotypes in humans and mice. We show here that recessive mutations of the gene encoding uracil-DNA glycosylase (UNG) are associated with profound impairment in CSR at a DNA precleavage step and with a partial disturbance of the SHM pattern in three patients with hyper-IgM syndrome. Together with the finding that nuclear UNG expression was induced in activated B cells, these data support a model of CSR and SHM in which AID deaminates cytosine into uracil in targeted DNA (immunoglobulin switch or variable regions), followed by uracil removal by UNG.

Randomized clinical trial of lumbar instrumented fusion and cognitive intervention and exercises in patients with chronic low back pain and disc degeneration

Abstract: Study design Single blind randomized study. Objectives To compare the effectiveness of lumbar instrumented fusion with cognitive intervention and exercises in patients with chronic low back pain and disc degeneration. Summary of background data To the authors' best knowledge, only one randomized study has evaluated the effectiveness of lumbar fusion. The Swedish Lumbar Spine Study reported that lumbar fusion was better than continuing physiotherapy and care by the family physician. Patients and methods Sixty-four patients aged 25-60 years with low back pain lasting longer than 1 year and evidence of disc degeneration at L4-L5 and/or L5-S1 at radiographic examination were randomized to either lumbar fusion with posterior transpedicular screws and postoperative physiotherapy, or cognitive intervention and exercises. The cognitive intervention consisted of a lecture to give the patient an understanding that ordinary physical activity would not harm the disc and a recommendation to use the back and bend it. This was reinforced by three daily physical exercise sessions for 3 weeks. The main outcome measure was the Oswestry Disability Index. Results At the 1-year follow-up visit, 97% of the patients, including 6 patients who had either not attended treatment or changed groups, were examined. The Oswestry Disability Index was significantly reduced from 41 to 26 after surgery, compared with 42 to 30 after cognitive intervention and exercises. The mean difference between groups was 2.3 (-6.7 to 11.4) (P = 0.33). Improvements inback pain, use of analgesics, emotional distress, life satisfaction, and return to work were not different. Fear-avoidance beliefs and fingertip-floor distance were reduced more after nonoperative treatment, and lower limb pain was reduced more after surgery. The success rate according to an independent observer was 70% after surgery and 76% after cognitive intervention and exercises. The early complication rate in the surgical group was 18%. Conclusion The main outcome measure showed equal improvement in patients with chronic low back pain and disc degeneration randomized to cognitive intervention and exercises, or lumbar fusion.

Human and bacterial oxidative demethylases repair alkylation damage in both RNA and DNA

Abstract: Repair of DNA damage is essential for maintaining genome integrity, and repair deficiencies in mammals are associated with cancer, neurological disease and developmental defects1. Alkylation damage in DNA is repaired by at least three different mechanisms, including damage reversal by oxidative demethylation of 1-methyladenine and 3-methylcytosine by Escherichia coli AlkB2,3. By contrast, little is known about consequences and cellular handling of alkylation damage to RNA4. Here we show that two human AlkB homologues, hABH2 and hABH3, also are oxidative DNA demethylases and that AlkB and hABH3, but not hABH2, also repair RNA. Whereas AlkB and hABH3 prefer single-stranded nucleic acids, hABH2 acts more efficiently on double-stranded DNA. In addition, AlkB and hABH3 expressed in E. coli reactivate methylated RNA bacteriophage MS2 in vivo, illustrating the biological relevance of this repair activity and establishing RNA repair as a potentially important defence mechanism in living cells. The different catalytic properties and the different subnuclear localization patterns shown by the human homologues indicate that hABH2 and hABH3 have distinct roles in the cellular response to alkylation damage.

The interacting pathways for prevention and repair of oxidative DNA damage.

Abstract: Genomes are damaged by spontaneous decay, chemicals, radiation and replication errors. DNA damage may cause mutations resulting in inheritable disease, cancer and ageing. Oxidative stress from ionising radiation and oxidative metabolism causes base damage, as well as strand breaks in DNA. Base damage is mostly indirect and caused by reactive oxygen species (ROS) generated, e.g. O2(.-) (superoxide radical), OH. (hydroxyl radical) and H2O2 (hydrogen peroxide). ROS also oxidise RNA, lipids, proteins and nucleotides. The first line of defence against ROS is enzymatic inactivation of superoxide by superoxide dismutase and inactivation of the less toxic hydrogen peroxide by catalase. As a second line of defence, incorporation of damaged bases into DNA is prevented by enzymes that hydrolyse oxidised dNTPs (e.g. 8-oxodGTP) to the corresponding dNMP. The third line of defence is repair of oxidative damage in DNA by an intricate network of DNA repair mechanisms. Base excision repair (BER), transcription-coupled repair (TCR), global genome repair (GGR), mismatch repair (MMR), translesion synthesis (TLS), homologous recombination (HR) and non-homologous end-joining (NHEJ) all contribute to repair of oxidative DNA damage. These mechanisms are also integrated with other cellular processes such as cell cycle regulation, transcription and replication and even use some common proteins. BER is the major pathway for repair of oxidative base damage, with TCR and MMR being important backup pathways for repair of transcribed strands and newly replicated strands, respectively. In recent years, several new DNA glycosylases that initiate BER of oxidative damage have been identified. These have specificities overlapping with previously known DNA glycosylases and serve as backups, and may have distinct roles as well. Thus, there is both inter- and intra-pathway complementation in repair of oxidative base damage, explaining the limited effects of absence of single DNA glycosylases in animal model systems.

Climate change and Arctic ecosystems: 2. Modeling, paleodata‐model comparisons, and future projections

Abstract: Large variations in the composition, structure, and function of Arctic ecosystems are determined by climatic gradients, especially of growing-season warmth, soil moisture, and snow cover. A unified circumpolar classification recognizing five types of tundra was developed. The geographic distributions of vegetation types north of 55degreesN, including the position of the forest limit and the distributions of the tundra types, could be predicted from climatology using a small set of plant functional types embedded in the biogeochemistry-biogeography model BIOME4. Several palaeoclimate simulations for the last glacial maximum (LGM) and mid-Holocene were used to explore the possibility of simulating past vegetation patterns, which are independently known based on pollen data. The broad outlines of observed changes in vegetation were captured. LGM simulations showed the major reduction of forest, the great extension of graminoid and forb tundra, and the restriction of low- and high-shrub tundra (although not all models produced sufficiently dry conditions to mimic the full observed change). Mid-Holocene simulations reproduced the contrast between northward forest extension in western and central Siberia and stability of the forest limit in Beringia. Projection of the effect of a continued exponential increase in atmospheric CO2 concentration, based on a transient ocean-atmosphere simulation including sulfate aerosol effects, suggests a potential for larger changes in Arctic ecosystems during the 21st century than have occurred between mid-Holocene and present. Simulated physiological effects of the CO2 increase (to >700 ppm) at high latitudes were slight compared with the effects of the change in climate.

Elements of a neurobiological theory of the hippocampus: the role of activity-dependent synaptic plasticity in memory

Abstract: The hypothesis that synaptic plasticity is a critical component of the neural mechanisms underlying learning and memory is now widely accepted. In this article, we begin by outlining four criteria for evaluating the 'synaptic plasticity and memory (SPM)' hypothesis. We then attempt to lay the foundations for a specific neurobiological theory of hippocampal (HPC) function in which activity-dependent synaptic plasticity, such as long-term potentiation (LTP), plays a key part in the forms of memory mediated by this brain structure. HPC memory can, like other forms of memory, be divided into four processes: encoding, storage, consolidation and retrieval. We argue that synaptic plasticity is critical for the encoding and intermediate storage of memory traces that are automatically recorded in the hippocampus. These traces decay, but are sometimes retained by a process of cellular consolidation. However, we also argue that HPC synaptic plasticity is not involved in memory retrieval, and is unlikely to be involved in systems-level consolidation that depends on HPC-neocortical interactions, although neocortical synaptic plasticity does play a part. The information that has emerged from the worldwide focus on the mechanisms of induction and expression of plasticity at individual synapses has been very valuable in functional studies. Progress towards a comprehensive understanding of memory processing will also depend on the analysis of these synaptic changes within the context of a wider range of systems-level and cellular mechanisms of neuronal transmission and plasticity.

A Heuristic for Moment-Matching Scenario Generation

Abstract: In stochastic programming models we always face the problem of how to represent the random variables. This is particularly difficult with multidimensional distributions. We present an algorithm that produces a discrete joint distribution consistent with specified values of the first four marginal moments and correlations. The joint distribution is constructed by decomposing the multivariate problem into univariate ones, and using an iterative procedure that combines simulation, Cholesky decomposition and various transformations to achieve the correct correlations without changing the marginal moments. With the algorithm, we can generate 1000 one-period scenarios for 12 random variables in 16 seconds, and for 20 random variables in 48 seconds, on a Pentium III machine.

Tracking control of an underactuated ship

Abstract: In this paper, we address the tracking problem for an underactuated ship using two controls, namely surge force and yaw moment. A simple state-feedback control law is developed and proved to render the tracking error dynamics globally K- exponentially stable. Experimental results are presented where the controller is implemented on a scale model of an offshore supply vessel.

Dynamic exchange coupling in magnetic bilayers.

Abstract: A long-range dynamic interaction between ferromagnetic films separated by normal-metal spacers is reported, which is communicated by nonequilibrium spin currents. It is measured by ferromagnetic resonance and explained by an adiabatic spin-pump theory. In such a resonance the spin-pump mechanism of spatially separated magnetic moments leads to an appreciable increase in the resonant linewidth when the resonance fields are well apart, and results in a dramatic linewidth narrowing when the resonant fields approach each other.

Depression and anxiety disorders associated with headache frequency. The Nord-Trøndelag Health Study.

Abstract: The aim of this large cross-sectional population-based study was to examine the association between migraine, non-migrainous headache and headache frequency with depression, and anxiety disorders. From 1995 to 1997, all 92 566 inhabitants aged 20 years and above in Nord-Trondelag County in Norway were invited to participate in the Nord-Trondelag Health Study ('Helseundersokelsen i Nord-Trondelag' = HUNT-2). A total of 64 560 participated, whereof 51 383 subjects (80%) completed a headache questionnaire that was included. Of these 51 383 individuals, 47 257 (92%) completed the depression subscale items and 43 478 (85%), the anxiety subscale items of the Hospital Anxiety and Depression Scale (HADS). Associations were assessed in multivariate analyses, estimating prevalence odds ratios (OR) with 95% confidence intervals (CI). Depression and anxiety disorders as measured by HADS, were significantly associated with migraine (OR = 2.7, 95% CI 2.3-3.2; OR = 3.2, 95% CI 2.8-3.6) and non-migrainous headache (OR = 2.2, 95% CI 2.0-2.5; OR = 2.7, 95% CI 2.4-3.0) when compared with headache-free individuals. The association was stronger for anxiety disorders than for depression. The ORs for depression and anxiety disorders amongst both migraine and non-migrainous sufferers increased with increasing headache frequency. Depression and anxiety disorders are associated with both migraine and non-migrainous headache, and this association seems more dependent on headache frequency than diagnostic category.

Climate change and Arctic ecosystems: 1. Vegetation changes north of 55°N between the last glacial maximum, mid‐Holocene, and present

Abstract: A unified scheme to assign pollen samples to vegetation types was used to reconstruct vegetation patterns north of 55°N at the last glacial maximum (LGM) and mid-Holocene (6000 years B.P.). The pollen data set assembled for this purpose represents a comprehensive compilation based on the work of many projects and research groups. Five tundra types (cushion forb tundra, graminoid and forb tundra, prostrate dwarf-shrub tundra, erect dwarf-shrub tundra, and low- and high-shrub tundra) were distinguished and mapped on the basis of modern pollen surface samples. The tundra-forest boundary and the distributions of boreal and temperate forest types today were realistically reconstructed. During the mid-Holocene the tundra-forest boundary was north of its present position in some regions, but the pattern of this shift was strongly asymmetrical around the pole, with the largest northward shift in central Siberia (∼200 km), little change in Beringia, and a southward shift in Keewatin and Labrador (∼200 km). Low- and high-shrub tundra extended farther north than today. At the LGM, forests were absent from high latitudes. Graminoid and forb tundra abutted on temperate steppe in northwestern Eurasia while prostrate dwarf-shrub, erect dwarf-shrub, and graminoid and forb tundra formed a mosaic in Beringia. Graminoid and forb tundra is restricted today and does not form a large continuous biome, but the pollen data show that it was far more extensive at the LGM, while low- and high-shrub tundra were greatly reduced, illustrating the potential for climate change to dramatically alter the relative areas occupied by different vegetation types.

Issues in using students in empirical studies in software engineering education

Abstract: Several empirical studies have been carried out with college students as subjects in the last few years. Researchers often use these studies to pilot experiments before they are carried out in industrial environments. Reports on these studies usually focus on the results obtained and issues such as their external validity. However, the effects and value of empirical studies with students may go beyond the contribution to scientific literature. For instance, the pedagogical challenges and value of these studies is hardly ever stressed. We identify four primary actors that are involved in these empirical studies, i.e., researchers, students, instructors, and industry. We discuss the costs and benefits of empirical studies with students for these actors, which are different because of the actors' different goals, expectations, and constraints, which must be recognized to fully exploit empirical studies with students. We also provide some advice on how to carry out empirical studies with students based on our experiences.

Prophylactic treatment of migraine with an angiotensin II receptor blocker: a randomized controlled trial.

Abstract: ContextThere is a paucity of effective, well-tolerated drugs available for migraine prophylaxis.ObjectiveTo determine whether treatment with the angiotensin II receptor blocker candesartan is effective as a migraine-prophylactic drug.Design and SettingRandomized, double-blind, placebo-controlled crossover study performed in a Norwegian neurological outpatient clinic from January 2001 to February 2002.PatientsSixty patients aged 18 to 65 years with 2 to 6 migraine attacks per month were recruited mainly from newspaper advertisements.InterventionsA placebo run-in period of 4 weeks was followed by two 12-week treatment periods separated by 4 weeks of placebo washout. Thirty patients were randomly assigned to receive one 16-mg candesartan cilexetil tablet daily in the first treatment period followed by 1 placebo tablet daily in the second period. The remaining 30 received placebo followed by candesartan.Main Outcome MeasuresThe primary end point was number of days with headache; secondary end points included hours with headache, days with migraine, hours with migraine, headache severity index, level of disability, doses of triptans, doses of analgesics, acceptability of treatment, days of sick leave, and quality-of-life variables on the Short Form 36 questionnaire.ResultsIn a period of 12 weeks, the mean number of days with headache was 18.5 with placebo vs 13.6 with candesartan (P = .001) in the intention-to-treat analysis (n = 57). Some secondary end points also favored candesartan, including hours with headache (139 vs 95; P<.001), days with migraine (12.6 vs 9.0; P<.001), hours with migraine (92.2 vs 59.4; P<.001), headache severity index (293 vs 191; P<.001), level of disability (20.6 vs 14.1; P<.001) and days of sick leave (3.9 vs 1.4; P = .01), although there were no significant differences in health-related quality of life. The number of candesartan responders (reduction of ≥50% compared with placebo) was 18 (31.6%) of 57 for days with headache and 23 (40.4%) of 57 for days with migraine. Adverse events were similar in the 2 periods.ConclusionIn this study, the angiotensin II receptor blocker candesartan provided effective migraine prophylaxis, with a tolerability profile comparable with that of placebo.

Euthanasia and physician-assisted suicide : a view from an EAPC ethics task force.

Abstract: In 1991, a debate at the European Parliament on euthanasia stimulated discussion at all levels in Europe. Subsequently, the Board of Directors of the EAPC organised a working session together with two experts to help them clarify the position the organisation should adopt towards euthanasia. The experts collaborated with the Board of Directors on a document and in 1994 the EAPC produced a first statement, Regarding euthanasia, published in the official journal of the EAPC – the European Journal of Palliative Care . In February 2001, the EAPC Board asked an expert group to form an Ethics Task Force to review the subject and advise the organisation accordingly.