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Search Results: 1 - 10 of 401404 matches for " Mick M. Welling "
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The Torus Universe in the Polygon Approach to 2+1-Dimensional Gravity
M. Welling
Physics , 1996, DOI: 10.1088/0264-9381/14/4/010
Abstract: In this paper we describe the matter-free toroidal spacetime in 't Hooft's polygon approach to 2+1-dimensional gravity (i.e. we consider the case without any particles present). Contrary to earlier results in the literature we find that it is not possible to describe the torus by just one polygon but we need at least two polygons. We also show that the constraint algebra of the polygons closes.
One Particle Hilbertspace of 2+1 dimensional Gravity using Non commuting Coordinates
M. Welling
Physics , 1997, DOI: 10.1016/S0920-5632(97)00368-X
Abstract: After a review of multi particle solutions in classical 2+1 dimensional gravity we will construct a one particle Hilbert space. As we will use a curved momentum space, the coordinates $x^\mu$ are represented as non commuting Hermitian operators on this Hilbertspace. Finally we will indicate how to construct a Schrodinger equation.
Two particle Quantummechanics in 2+1 Gravity using Non Commuting Coordinates
M. Welling
Physics , 1997, DOI: 10.1088/0264-9381/14/12/015
Abstract: We find that the momentum conjugate to the relative distance between two gravitating particles in their center of mass frame is a hyperbolic angle. This fact strongly suggests that momentum space should be taken to be a hyperboloid. We investigate the effect of quantization on this curved momentum space. The coordinates are represented by non commuting, Hermitian operators on this hyperboloid. We also find that there is a smallest distance between the two particles of one half times the Planck length.
Explicit solutions for Point Particles and Black Holes in spaces of constant curvature in 2+1-D Gravity
M. Welling
Physics , 1997, DOI: 10.1016/S0550-3213(98)00008-X
Abstract: In this paper we consider space-times containing matter expanding or contracting according to a time-dependent scale factor. Cosmologies with vanishing, positive or negative cosmological constant are considered. In the case of vanishing or negative cosmological constant open and closed spatial surfaces are solutions while in the case of positive cosmological constant only closed surfaces exist. The gravitational field is solved explicitly in the case of 1 or 2 particles, 1 black-hole, and 1 black-hole vacuum state.
Winding Solutions for the two Particle System in 2+1 Gravity
M. Welling
Physics , 1997, DOI: 10.1088/0264-9381/15/3/012
Abstract: Using a PASCAL program to follow the evolution of two gravitating particles in 2+1 dimensions we find solutions in which the particles wind around one another indefinitely. As their center of mass moves `tachyonic' they form a Gott-pair. To avoid unphysical boundary conditions we consider a large but closed universe. After the particles have evolved for some time their momenta have grown very large. In this limit we quantize the model and find that both the relevant configuration variable and its conjugate momentum become discrete.
In Vivo Detection of Amyloid-β Deposits Using Heavy Chain Antibody Fragments in a Transgenic Mouse Model for Alzheimer's Disease
Rob J. A. Nabuurs, Kim S. Rutgers, Mick M. Welling, Athanasios Metaxas, Maaike E. de Backer, Maarten Rotman, Brian J. Bacskai, Mark A. van Buchem, Silvère M. van der Maarel, Louise van der Weerd
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0038284
Abstract: This study investigated the in vivo properties of two heavy chain antibody fragments (VHH), ni3A and pa2H, to differentially detect vascular or parenchymal amyloid-β deposits characteristic for Alzheimer's disease and cerebral amyloid angiopathy. Blood clearance and biodistribution including brain uptake were assessed by bolus injection of radiolabeled VHH in APP/PS1 mice or wildtype littermates. In addition, in vivo specificity for Aβ was examined in more detail with fluorescently labeled VHH by circumventing the blood-brain barrier via direct application or intracarotid co-injection with mannitol. All VHH showed rapid renal clearance (10–20 min). Twenty-four hours post-injection 99mTc-pa2H resulted in a small yet significant higher cerebral uptake in the APP/PS1 animals. No difference in brain uptake were observed for 99mTc-ni3A or DTPA(111In)-pa2H, which lacked additional peptide tags to investigate further clinical applicability. In vivo specificity for Aβ was confirmed for both fluorescently labeled VHH, where pa2H remained readily detectable for 24 hours or more after injection. Furthermore, both VHH showed affinity for parenchymal and vascular deposits, this in contrast to human tissue, where ni3A specifically targeted only vascular Aβ. Despite a brain uptake that is as yet too low for in vivo imaging, this study provides evidence that VHH detect Aβ deposits in vivo, with high selectivity and favorable in vivo characteristics, making them promising tools for further development as diagnostic agents for the distinctive detection of different Aβ deposits.
Pauli-Lubanski scalar in the Polygon Approach to 2+1-Dimensional Gravity
M. Welling,M. Bijlsma
Physics , 1996, DOI: 10.1088/0264-9381/13/7/010
Abstract: In this paper we derive an expression for the conserved Pauli-Lubanski scalar in 't Hooft's polygon approach to 2+1-dimensional gravity coupled to point particles. We find that it is represented by an extra spatial shift $\Delta$ in addition to the usual identification rule (being a rotation over the cut). For two particles this invariant is expressed in terms of 't Hooft's phase-space variables and we check its classical limit.
Digitaal werk gaat niet door een versnipperaar
G.M. Welling
BMGN : Low Countries Historical Review , 2001,
Abstract: George M. Welling, The prize of neutrality. Trade relations between Amsterdam and North America 1771-1817. A study in computational history (Dissertatie Groningen 1998; Amsterdamse historische reeks. Kleine serie XXXIX; Amsterdam: Historisch Seminarium van de Universiteit van Amsterdam, 1998, 261 blz., ISBN 90 73941 21 0).
Using Database Metadata and its Semantics to Generate Automatic and Dynamic Web Entry Forms
Mohammed M. Elsheh,Mick J. Ridley
Lecture Notes in Engineering and Computer Science , 2007,
Differences in miRNA Expression in Early Stage Lung Adenocarcinomas that Did and Did Not Relapse
Mick D. Edmonds, Christine M. Eischen
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0101802
Abstract: Relapse of adenocarcinoma, the most common non-small cell lung cancer (NSCLC), is a major clinical challenge to improving survival. To gain insight into the early molecular events that contribute to lung adenocarcinoma relapse, and taking into consideration potential cell type specificity, we used stringent criteria for sample selection. We measured miRNA expression only from flash frozen stage I lung adenocarcinomas, excluding other NSCLC subtypes. We compared miRNA expression in lung adenocarcinomas that relapsed within two years to those that did not relapse within three years after surgical resection prior to adjuvant therapy. The most significant differences in mRNA expression for recurrent tumors compared to non-recurrent tumors were decreases in miR-106b*, -187, -205, -449b, -774* and increases in miR-151-3p, let-7b, miR-215, -520b, and -512-3p. A unique comparison between adjacent normal lung tissue from relapse and non-relapse groups revealed dramatically different miRNA expression, suggesting dysregulation of miRNA in the environment around the tumor. To assess patient-to-patient variability, miRNA levels in the tumors were normalized to levels in matched adjacent normal lung tissue. This analysis revealed a different set of significantly altered miRNA in tumors that recurred compared to tumors that did not. Together our analyses elucidated miRNA not previously linked to lung adenocarcinoma that likely have important roles in its development and progression. Our results also highlight the differences in miRNA expression in normal lung tissue in adenocarcinomas that do and do not recur. Most notably, our data identified those miRNA that distinguish early stage tumors likely to relapse prior to treatment and miRNA that could be further studied for use as biomarkers for prognosis, patient monitoring, and/or treatment decisions.
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