University of Iceland

About: University of Iceland is a education organization based out in Reykjavik, Suðurnes, Iceland. It is known for research contribution in the topics: Population & Genome-wide association study. The organization has 5423 authors who have published 16199 publications receiving 694762 citations. The organization is also known as: Háskóli Íslands.

Novel MITF Targets Identified Using a Two-Step DNA Microarray Strategy

Abstract: Malignant melanoma is a chemotherapy-resistant cancer with high mortality. Recent advances in our understanding of the disease at the molecular level have indicated that it shares many characteristics with developmental precursors to melanocytes, the mature pigment-producing cells of the skin and hair follicles. The development of melanocytes absolutely depends on the action of the microphthalmia-associated transcription factor (MITF). MITF has been shown to regulate a broad variety of genes, whose functions range from pigment production to cell-cycle regulation, migration and survival. However, the existing list of targets is not sufficient to explain the role of MITF in melanocyte development and melanoma progression. DNA microarray analysis of gene expression offers a straightforward approach to identify new target genes, but standard analytical procedures are susceptible to the generation of false positives and require additional experimental steps for validation. Here, we introduce a new strategy where two DNA microarray-based approaches for identifying transcription factor targets are combined in a cross-validation protocol designed to help control false-positive generation. We use this two-step approach to successfully re-identify thirteen previously recorded targets of MITF-mediated upregulation, as well as 71 novel targets. Many of these new targets have known relevance to pigmentation and melanoma biology, and further emphasize the critical role of MITF in these processes.

CFH Y402H Confers Similar Risk of Soft Drusen and Both Forms of Advanced AMD

Abstract: Background Age-related macular degeneration (AMD) is the most common cause of irreversible visual impairment in the developed world. The two forms of advanced AMD, geographic atrophy and neovascular AMD, represent different pathological processes in the macula that lead to loss of central vision. Soft drusen, characterized by deposits in the macula without visual loss, are considered to be a precursor of advanced AMD. Recently, it has been proposed that a common missense variant, Y402H, in the Complement Factor H (CFH) gene increases the risk for advanced AMD. However, its impact on soft drusen, GA, or neovascular AMD—or the relationship between them—is unclear.

Multilevel Image Segmentation Based on Fractional-Order Darwinian Particle Swarm Optimization

Abstract: Hyperspectral remote sensing images contain hundreds of data channels. Due to the high dimensionality of the hyperspectral data, it is difficult to design accurate and efficient image segmentation algorithms for such imagery. In this paper, a new multilevel thresholding method is introduced for the segmentation of hyperspectral and multispectral images. The new method is based on fractional-order Darwinian particle swarm optimization (FODPSO) which exploits the many swarms of test solutions that may exist at any time. In addition, the concept of fractional derivative is used to control the convergence rate of particles. In this paper, the so-called Otsu problem is solved for each channel of the multispectral and hyperspectral data. Therefore, the problem of n-level thresholding is reduced to an optimization problem in order to search for the thresholds that maximize the between-class variance. Experimental results are favorable for the FODPSO when compared to other bioinspired methods for multilevel segmentation of multispectral and hyperspectral images. The FODPSO presents a statistically significant improvement in terms of both CPU time and fitness value, i.e., the approach is able to find the optimal set of thresholds with a larger between-class variance in less computational time than the other approaches. In addition, a new classification approach based on support vector machine (SVM) and FODPSO is introduced in this paper. Results confirm that the new segmentation method is able to improve upon results obtained with the standard SVM in terms of classification accuracies.

The optical afterglow of the short gamma-ray burst associated with GW170817

Abstract: The binary neutron star merger GW170817 was the first multi-messenger event observed in both gravitational and electromagnetic waves1,2. The electromagnetic signal began approximately two seconds post-merger with a weak, short burst of gamma rays3, which was followed over the next hours and days by the ultraviolet, optical and near-infrared emission from a radioactively powered kilonova4,5,6,7,8,9,10,11. Later, non-thermal rising X-ray and radio emission was observed12,13. The low luminosity of the gamma rays and the rising non-thermal flux from the source at late times could indicate that we are outside the opening angle of the beamed relativistic jet. Alternatively, the emission could be arising from a cocoon of material formed from the interaction between a jet and the merger ejecta13,14,15. Here we present late-time optical detections and deep near-infrared limits on the emission from GW170817 at 110 days post-merger. Our new observations are at odds with expectations of late-time emission from kilonova models, being too bright and blue16,17. Instead, the emission arises from the interaction between the relativistic ejecta of GW170817 and the interstellar medium. We show that this emission matches the expectations of a Gaussian-structured relativistic jet, which would have launched a high-luminosity, short gamma-ray burst to an aligned observer. However, other jet structure or cocoon models can also match current data—the future evolution of the afterglow will directly distinguish the origin of the emission.

Mandibular third molar removal: Risk indicators for extended operation time, postoperative pain, and complications

Abstract: Objectives The aim of this study was to identify risk indicators for extended operation time and postoperative complications after removal of mandibular third molars. Study design There were 388 molars included in the study. The teeth were removed using the buccal approach under local anesthesia. Four hours postoperatively the patient recorded his or her pain perception on a visual analogue scale (VAS). After surgery a surgeon recorded parameters regarding the tooth and if the mandibular nerve had been visible during the operation. One week postoperatively the postoperative pain and complications were recorded. Logistic regression models were made to identify risk indicators for extended operation time, postoperative pain, and complications. Results Females were at higher risk for postoperative pain and dry socket than males. Older patients were at higher risk for extended operation time than younger patients. Radiographically fully impacted molars increased the risk of postoperative general infection. If the nerve was visible during surgery there was a higher risk of a high VAS score, postoperative pain, and general infection than if the nerve had not been visible. Conclusion Several indicators were found to increase the risk of postoperative complications, but a visible alveolar inferior nerve during the operation was repeatedly found to be the highest single risk indicator.